When switching between AIO contexts we need to me make sure that both
recv_coroutine and send_coroutine are not scheduled to run. Otherwise,
QEMU may crash while attaching the new context with an error like
this one:
aio_co_schedule: Co-routine was already scheduled in 'aio_co_schedule'
To achieve this we need a local implementation of
'qio_channel_readv_all_eof' named 'nbd_read_eof' (a trick already done
by 'nbd/client.c') that allows us to interrupt the operation and to
know when recv_coroutine is yielding.
With this in place, we delegate detaching the AIO context to the
owning context with a BH ('nbd_aio_detach_bh') scheduled using
'aio_wait_bh_oneshot'. This BH signals that we need to quiesce the
channel by setting 'client->quiescing' to 'true', and either waits for
the coroutine to finish using AIO_WAIT_WHILE or, if it's yielding in
'nbd_read_eof', actively enters the coroutine to interrupt it.
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1900326
Signed-off-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201214170519.223781-4-slp@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Coverity noticed (CID 1436125) that we check the return value of
nbd_extent_array_add in most places, but not at the end of
bitmap_to_extents(). The return value exists to break loops before a
future iteration, so there is nothing to check if we are already done
iterating. Adding a cast to void, plus a comment why, pacifies
Coverity.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201111163510.713855-1-eblake@redhat.com>
[eblake: Prefer cast to void over odd && usage]
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Allow the server to expose an additional metacontext to be requested
by savvy clients. qemu-nbd adds a new option -A to expose the
qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
can also be set via QMP when using block-export-add.
qemu as client is hacked into viewing the key aspects of this new
context by abusing the already-experimental x-dirty-bitmap option to
collapse all depths greater than 2, which results in a tri-state value
visible in the output of 'qemu-img map --output=json' (yes, that means
x-dirty-bitmap is now a bit of a misnomer, but I didn't feel like
renaming it as it would introduce a needless break of back-compat,
even though we make no compat guarantees with x- members):
unallocated (depth 0) => "zero":false, "data":true
local (depth 1) => "zero":false, "data":false
backing (depth 2+) => "zero":true, "data":true
libnbd as client is probably a nicer way to get at the information
without having to decipher such hacks in qemu as client. ;)
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-11-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
'qemu-img map' provides a way to determine which extents of an image
come from the top layer vs. inherited from a backing chain. This is
useful information worth exposing over NBD. There is a proposal to
add a QMP command block-dirty-bitmap-populate which can create a dirty
bitmap that reflects allocation information, at which point the
qemu:dirty-bitmap:NAME metadata context can expose that information
via the creation of a temporary bitmap, but we can shorten the effort
by adding a new qemu:allocation-depth metadata context that does the
same thing without an intermediate bitmap (this patch does not
eliminate the need for that proposal, as it will have other uses as
well).
While documenting things, remember that although the NBD protocol has
NBD_OPT_SET_META_CONTEXT, the rest of its documentation refers to
'metadata context', which is a more apt description of what is
actually being used by NBD_CMD_BLOCK_STATUS: the user is requesting
metadata by passing one or more context names. So I also touched up
some existing wording to prefer the term 'metadata context' where it
makes sense.
Note that this patch does not actually enable any way to request a
server to enable this context; that will come in the next patch.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-10-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
With this, 'qemu-nbd -B b0 -B b1 -f qcow2 img.qcow2' can let you sniff
out multiple bitmaps from one server. qemu-img as client can still
only read one bitmap per client connection, but other NBD clients
(hello libnbd) can now read multiple bitmaps in a single pass.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201027050556.269064-8-eblake@redhat.com>
Rather than open-code the count of negotiated contexts at several
sites, embed it directly into the struct. This will make it easier
for upcoming commits to support even more simultaneous contexts.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-7-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Each dirty bitmap already knows its name; by reducing the scope of the
places where we construct "qemu:dirty-bitmap:NAME" strings, tracking
the name is more localized, and there are fewer per-export fields to
worry about. This in turn will make it easier for an upcoming patch
to export more than one bitmap at once.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201027050556.269064-6-eblake@redhat.com>
Since 'block-export-add' is new to 5.2, we can still tweak the
interface; there, allowing 'bitmaps':['str'] is nicer than
'bitmap':'str'. This wires up the qapi and qemu-nbd changes to permit
passing multiple bitmaps as distinct metadata contexts that the NBD
client may request, but the actual support for more than one will
require a further patch to the server.
Note that there are no changes made to the existing deprecated
'nbd-server-add' command; this required splitting the QAPI type
BlockExportOptionsNbd, which fortunately does not affect QMP
introspection.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Make it possible to specify the iothread where the export will run. By
default the block node can be moved to other AioContexts later and the
export will follow. The fixed-iothread option forces strict behavior
that prevents changing AioContext while the export is active. See the
QAPI docs for details.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200929125516.186715-5-stefanha@redhat.com
[Fix stray '#' character in block-export.json and add missing "(since:
5.2)" as suggested by Eric Blake.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
We had a premature optimization of trying to read as little from the
wire as possible while handling NBD_OPT_SET_META_CONTEXT in phases.
But in reality, we HAVE to read the entire string from the client
before we can get to the next command, and it is easier to just read
it all at once than it is to read it in pieces. And once we do that,
several functions end up no longer performing I/O, so they can drop
length and errp parameters, and just return a bool instead of
modifying through a pointer.
Our iotests still pass; I also checked that libnbd's testsuite (which
covers more corner cases of odd meta context requests) still passes.
There are cases where the sequence of trace messages produced differs
(for example, when no bitmap is exported, a query for "qemu:" now
produces two trace lines instead of one), but trace points are for
debug and have no effect on what the client sees.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200930121105.667049-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: enhance commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NBD spec is clear that any string sent from the client must not
contain embedded NUL characters. If the client passes "a\0", we
should reject that option request rather than act on "a".
Testing this is not possible with a compliant client, but I was able
to use gdb to coerce libnbd into temporarily behaving as such a
client.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200930121105.667049-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
gcc 10 from Fedora 32 gives me:
Compiling C object libblock.fa.p/nbd_server.c.o
../nbd/server.c: In function ‘nbd_co_client_start’:
../nbd/server.c:625:14: error: ‘namelen’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
625 | rc = nbd_negotiate_send_info(client, NBD_INFO_NAME, namelen, name,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
626 | errp);
| ~~~~~
../nbd/server.c:564:14: note: ‘namelen’ was declared here
564 | uint32_t namelen;
| ^~~~~~~
cc1: all warnings being treated as errors
As I cannot see how this can happen, let uns silence the warning.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20200930155859.303148-3-borntraeger@de.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
There is no real reason any more why nbd_export_new() and
nbd_export_create() should be separate functions. The latter only
performs a few checks before it calls the former.
What makes the current state stand out is that it's the only function in
BlockExportDriver that is not a static function inside nbd/server.c, but
a small wrapper in blockdev-nbd.c that then calls back into nbd/server.c
for the real functionality.
Move all the checks to nbd/server.c and make the resulting function
static to improve readability.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-27-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The 'writable' option is a basic option that will probably be applicable
to most if not all export types that we will implement. Move it from NBD
to the generic BlockExport layer.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-26-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Every export type will need a BlockBackend, so creating it centrally in
blk_exp_add() instead of the .create driver callback avoids duplication.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-24-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Every block export has a BlockBackend representing the disk that is
exported. It should live in BlockExport therefore.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-23-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Implement a new QMP command block-export-del and make nbd-server-remove
a wrapper around it.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-21-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The reference owned by the user/monitor that is created when adding the
export and dropped when removing it was tied to the 'exports' list in
nbd/server.c. Every block export will have a user reference, so move it
to the block export level and tie it to the 'block_exports' list in
block/export/export.c instead. This is necessary for introducing a QMP
command for removing exports.
Note that exports are present in block_exports even after the user has
requested shutdown. This is different from NBD's exports where exports
are immediately removed on a shutdown request, even if they are still in
the process of shutting down. In order to avoid that the user still
interacts with an export that is shutting down (and possibly removes it
a second time), we need to remember if the user actually still owns it.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-20-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This adds a function to shut down all block exports, and another one to
shut down the block exports of a single type. The latter is used for now
when stopping the NBD server. As soon as we implement support for
multiple NBD servers, we'll need a per-server list of exports and it
will be replaced by a function using that.
As a side effect, the BlockExport layer has a list tracking all existing
exports now. closed_exports loses its only user and can go away.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-18-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Instead of letting the driver allocate and return the BlockExport
object, allocate it already in blk_exp_add() and pass it. This allows us
to initialise the generic part before calling into the driver so that
the driver can just use these values instead of having to parse the
options a second time.
For symmetry, move freeing the BlockExport to blk_exp_unref().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-17-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-15-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Having a refcount makes sense for all types of block exports. It is also
a prerequisite for keeping a list of all exports at the BlockExport
level.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-14-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Closing export is somewhat convoluted because nbd_export_close() and
nbd_export_put() call each other and the ways they actually end up being
nested is not necessarily obvious.
However, it is not really necessary to call nbd_export_close() from
nbd_export_put() when putting the last reference because it only does
three things:
1. Close all clients. We're going to refcount 0 and all clients hold a
reference, so we know there is no active client any more.
2. Close the user reference (represented by exp->name being non-NULL).
The same argument applies: If the export were still named, we would
still have a reference.
3. Freeing exp->description. This is really cleanup work to be done when
the export is finally freed. There is no reason to already clear it
while clients are still in the process of shutting down.
So after moving the cleanup of exp->description, the code can be
simplified so that only nbd_export_close() calls nbd_export_put(), but
never the other way around.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-13-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The export close callback is unused by the built-in NBD server. qemu-nbd
uses it only during shutdown to wait for the unrefed export to actually
go away. It can just use nbd_export_close_all() instead and do without
the callback.
This removes the close callback from nbd_export_new() and makes both
callers of it more similar.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-11-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
nbd-server-add tries to be convenient and adds two questionable
features that we don't want to share in block-export-add, even for NBD
exports:
1. When requesting a writable export of a read-only device, the export
is silently downgraded to read-only. This should be an error in the
context of block-export-add.
2. When using a BlockBackend name, unplugging the device from the guest
will automatically stop the NBD server, too. This may sometimes be
what you want, but it could also be very surprising. Let's keep
things explicit with block-export-add. If the user wants to stop the
export, they should tell us so.
Move these things into the nbd-server-add QMP command handler so that
they apply only there.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-8-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Instead of implementing qemu-nbd --offset in the NBD code, just put a
raw block node with the requested offset on top of the user image and
rely on that doing the job.
This does not only simplify the nbd_export_new() interface and bring it
closer to the set of options that the nbd-server-add QMP command offers,
but in fact it also eliminates a potential source for bugs in the NBD
code which previously had to add the offset manually in all relevant
places.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-7-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We want to have a common set of commands for all types of block exports.
Currently, this is only NBD, but we're going to add more types.
This patch adds the basic BlockExport and BlockExportDriver structs and
a QMP command block-export-add that creates a new export based on the
given BlockExportOptions.
qmp_nbd_server_add() becomes a wrapper around qmp_block_export_add().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-5-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-2-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When looking for a dirty bitmap to share, we should handle filters by
just including them in the search (so they do not break backing chains).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Although qemu as NBD client limits requests to <2G, the NBD protocol
allows clients to send requests almost all the way up to 4G. But
because our block layer is not yet 64-bit clean, we accidentally wrap
such requests into a negative size, and fail with EIO instead of
performing the intended operation.
The bug is visible in modern systems with something as simple as:
$ qemu-img create -f qcow2 /tmp/image.img 5G
$ sudo qemu-nbd --connect=/dev/nbd0 /tmp/image.img
$ sudo blkdiscard /dev/nbd0
or with user-space only:
$ truncate --size=3G file
$ qemu-nbd -f raw file
$ nbdsh -u nbd://localhost:10809 -c 'h.trim(3*1024*1024*1024,0)'
Although both blk_co_pdiscard and blk_pwrite_zeroes currently return 0
on success, this is also a good time to fix our code to a more robust
paradigm that treats all non-negative values as success.
Alas, our iotests do not currently make it easy to add external
dependencies on blkdiscard or nbdsh, so we have to rely on manual
testing for now.
This patch can be reverted when we later improve the overall block
layer to be 64-bit clean, but for now, a minimal fix was deemed less
risky prior to release.
CC: qemu-stable@nongnu.org
Fixes: 1f4d6d18ed
Fixes: 1c6c4bb7f0
Fixes: https://github.com/systemd/systemd/issues/16242
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200722212231.535072-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: rework success tests to use >=0]
Consider nbd_export_close_all(). The call-stack looks like this:
nbd_export_close_all() -> nbd_export_close -> call client_close() for
each client.
client_close() doesn't guarantee that client is closed: nbd_trip()
keeps reference to it. So, nbd_export_close_all() just reduce
reference counter on export and removes it from the list, but doesn't
guarantee that nbd_trip() finished neither export actually removed.
Let's wait for all exports actually removed.
Without this fix, the following crash is possible:
- export bitmap through internal Qemu NBD server
- connect a client
- shutdown Qemu
On shutdown nbd_export_close_all is called, but it actually don't wait
for nbd_trip() to finish and to release its references. So, export is
not release, and exported bitmap remains busy, and on try to remove the
bitmap (which is part of bdrv_close()) the assertion fails:
bdrv_release_dirty_bitmap_locked: Assertion `!bdrv_dirty_bitmap_busy(bitmap)' failed
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200714162234.13113-2-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If we want to check error after errp-function call, we need to
introduce local_err and then propagate it to errp. Instead, use
the ERRP_GUARD() macro, benefits are:
1. No need of explicit error_propagate call
2. No need of explicit local_err variable: use errp directly
3. ERRP_GUARD() leaves errp as is if it's not NULL or
&error_fatal, this means that we don't break error_abort
(we'll abort on error_set, not on error_propagate)
If we want to add some info to errp (by error_prepend() or
error_append_hint()), we must use the ERRP_GUARD() macro.
Otherwise, this info will not be added when errp == &error_fatal
(the program will exit prior to the error_append_hint() or
error_prepend() call). Fix several such cases, e.g. in nbd_read().
This commit is generated by command
sed -n '/^Network Block Device (NBD)$/,/^$/{s/^F: //p}' \
MAINTAINERS | \
xargs git ls-files | grep '\.[hc]$' | \
xargs spatch \
--sp-file scripts/coccinelle/errp-guard.cocci \
--macro-file scripts/cocci-macro-file.h \
--in-place --no-show-diff --max-width 80
Reported-by: Kevin Wolf <kwolf@redhat.com>
Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200707165037.1026246-8-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[ERRP_AUTO_PROPAGATE() renamed to ERRP_GUARD(), and
auto-propagated-errp.cocci to errp-guard.cocci. Commit message
tweaked again.]
Ever since commit 36683283 (v2.8), the server code asserts that error
strings sent to the client are well-formed per the protocol by not
exceeding the maximum string length of 4096. At the time the server
first started sending error messages, the assertion could not be
triggered, because messages were completely under our control.
However, over the years, we have added latent scenarios where a client
could trigger the server to attempt an error message that would
include the client's information if it passed other checks first:
- requesting NBD_OPT_INFO/GO on an export name that is not present
(commit 0cfae925 in v2.12 echoes the name)
- requesting NBD_OPT_LIST/SET_META_CONTEXT on an export name that is
not present (commit e7b1948d in v2.12 echoes the name)
At the time, those were still safe because we flagged names larger
than 256 bytes with a different message; but that changed in commit
93676c88 (v4.2) when we raised the name limit to 4096 to match the NBD
string limit. (That commit also failed to change the magic number
4096 in nbd_negotiate_send_rep_err to the just-introduced named
constant.) So with that commit, long client names appended to server
text can now trigger the assertion, and thus be used as a denial of
service attack against a server. As a mitigating factor, if the
server requires TLS, the client cannot trigger the problematic paths
unless it first supplies TLS credentials, and such trusted clients are
less likely to try to intentionally crash the server.
We may later want to further sanitize the user-supplied strings we
place into our error messages, such as scrubbing out control
characters, but that is less important to the CVE fix, so it can be a
later patch to the new nbd_sanitize_name.
Consideration was given to changing the assertion in
nbd_negotiate_send_rep_verr to instead merely log a server error and
truncate the message, to avoid leaving a latent path that could
trigger a future CVE DoS on any new error message. However, this
merely complicates the code for something that is already (correctly)
flagging coding errors, and now that we are aware of the long message
pitfall, we are less likely to introduce such errors in the future,
which would make such error handling dead code.
Reported-by: Xueqiang Wei <xuwei@redhat.com>
CC: qemu-stable@nongnu.org
Fixes: https://bugzilla.redhat.com/1843684 CVE-2020-10761
Fixes: 93676c88d7
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200610163741.3745251-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Use bdrv_dirty_bitmap_next_dirty_area for bitmap_to_extents. Since
bdrv_dirty_bitmap_next_dirty_area is very accurate in its interface,
we'll never exceed requested region with last chunk. So, we don't need
dont_fragment, and bitmap_to_extents() interface becomes clean enough
to not require any comment.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20200205112041.6003-10-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
Introduce NBDExtentArray class, to handle extents list creation in more
controlled way and with fewer OUT parameters in functions.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20200205112041.6003-9-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
We are going to introduce bdrv_dirty_bitmap_next_dirty so that same
variable may be used to store its return value and to be its parameter,
so it would int64_t.
Similarly, we are going to refactor hbitmap_next_dirty_area to use
hbitmap_next_dirty together with hbitmap_next_zero, therefore we want
hbitmap_next_zero parameter type to be int64_t too.
So, for convenience update all parameters of *_next_zero and
*_next_dirty_area to be int64_t.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20200205112041.6003-6-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>
Detected by a hang in the libnbd testsuite. If a client requests
multiple meta contexts (both base:allocation and qemu:dirty-bitmap:x)
at the same time, our attempt to silence a false-positive warning
about a potential uninitialized variable introduced botched logic: we
were short-circuiting the second context, and never sending the
NBD_REPLY_FLAG_DONE. Combining two 'if' into one 'if/else' in
bdf200a55 was wrong (I'm a bit embarrassed that such a change was my
initial suggestion after the v1 patch, then I did not review the v2
patch that actually got committed). Revert that, and instead silence
the false positive warning by replacing 'return ret' with 'return 0'
(the value it always has at that point in the code, even though it
eluded the deduction abilities of the robot that reported the false
positive).
Fixes: bdf200a553
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200206173832.130004-1-eblake@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Fixes:
/mnt/sdb/qemu/nbd/server.c: In function 'nbd_handle_request':
/mnt/sdb/qemu/nbd/server.c:2313:9: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]
int ret;
Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200108025132.46956-1-pannengyuan@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Qemu as server currently won't accept export names larger than 256
bytes, nor create dirty bitmap names longer than 1023 bytes, so most
uses of qemu as client or server have no reason to get anywhere near
the NBD spec maximum of a 4k limit per string.
However, we weren't actually enforcing things, ignoring when the
remote side violates the protocol on input, and also having several
code paths where we send oversize strings on output (for example,
qemu-nbd --description could easily send more than 4k). Tighten
things up as follows:
client:
- Perform bounds check on export name and dirty bitmap request prior
to handing it to server
- Validate that copied server replies are not too long (ignoring
NBD_INFO_* replies that are not copied is not too bad)
server:
- Perform bounds check on export name and description prior to
advertising it to client
- Reject client name or metadata query that is too long
- Adjust things to allow full 4k name limit rather than previous
256 byte limit
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20191114024635.11363-4-eblake@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
As long as we limit NBD names to 256 bytes (the bare minimum permitted
by the standard), stack-allocation works for parsing a name received
from the client. But as mentioned in a comment, we eventually want to
permit up to the 4k maximum of the NBD standard, which is too large
for stack allocation; so switch everything in the server to use heap
allocation. For now, there is no change in actually supported name
length.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20191114024635.11363-2-eblake@redhat.com>
[eblake: fix uninit variable compile failure]
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
When iothreads are in use, the failure to grab the aio context results
in an assertion failure when trying to unlock things during blk_unref,
when trying to unlock a mutex that was not locked. In short, all
calls to nbd_export_put need to done while within the correct aio
context. But since nbd_export_put can recursively reach itself via
nbd_export_close, and recursively grabbing the context would deadlock,
we can't do the context grab directly in those functions, but must do
so in their callers.
Hoist the use of the correct aio_context from nbd_export_new() to its
caller qmp_nbd_server_add(). Then tweak qmp_nbd_server_remove(),
nbd_eject_notifier(), and nbd_esport_close_all() to grab the right
context, so that all callers during qemu now own the context before
nbd_export_put() can call blk_unref().
Remaining uses in qemu-nbd don't matter (since that use case does not
support iothreads).
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190917023917.32226-1-eblake@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
On creation, the export's AioContext is set to the same one as the
BlockBackend, while the AioContext in the client QIOChannel is left
untouched.
As a result, when using data-plane, nbd_client_receive_next_request()
schedules coroutines in the IOThread AioContext, while the client's
QIOChannel is serviced from the main_loop, potentially triggering the
assertion at qio_channel_restart_[read|write].
To fix this, as soon we have the export corresponding to the client,
we call qio_channel_attach_aio_context() to attach the QIOChannel
context to the export's AioContext. This matches with the logic at
blk_aio_attached().
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20190912110032.26395-1-slp@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The server side is fairly straightforward: we can always advertise
support for detection of fast zero, and implement it by mapping the
request to the block layer BDRV_REQ_NO_FALLBACK.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: update iotests 223, 233]
Commit fe0480d6 and friends added BDRV_REQ_NO_FALLBACK as a way to
avoid wasting time on a preliminary write-zero request that will later
be rewritten by actual data, if it is known that the write-zero
request will use a slow fallback; but in doing so, could not optimize
for NBD. The NBD specification is now considering an extension that
will allow passing on those semantics; this patch updates the new
protocol bits and 'qemu-nbd --list' output to recognize the bit, as
well as the new errno value possible when using the new flag; while
upcoming patches will improve the client to use the feature when
present, and the server to advertise support for it.
The NBD spec recommends (but not requires) that ENOTSUP be avoided for
all but failures of a fast zero (the only time it is mandatory to
avoid an ENOTSUP failure is when fast zero is supported but not
requested during write zeroes; the questionable use is for ENOTSUP to
other actions like a normal write request). However, clients that get
an unexpected ENOTSUP will either already be treating it the same as
EINVAL, or may appreciate the extra bit of information. We were
equally loose for returning EOVERFLOW in more situations than
recommended by the spec, so if it turns out to be a problem in
practice, a later patch can tighten handling for both error codes.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: tweak commit message, also handle EOPNOTSUPP]
When creating a read-only image, we are still advertising support for
TRIM and WRITE_ZEROES to the client, even though the client should not
be issuing those commands. But seeing this requires looking across
multiple functions:
All callers to nbd_export_new() passed a single flag based solely on
whether the export allows writes. Later, we then pass a constant set
of flags to nbd_negotiate_options() (namely, the set of flags which we
always support, at least for writable images), which is then further
dynamically modified with NBD_FLAG_SEND_DF based on client requests
for structured options. Finally, when processing NBD_OPT_EXPORT_NAME
or NBD_OPT_EXPORT_GO we bitwise-or the original caller's flag with the
runtime set of flags we've built up over several functions.
Let's refactor things to instead compute a baseline of flags as soon
as possible which gets shared between multiple clients, in
nbd_export_new(), and changing the signature for the callers to pass
in a simpler bool rather than having to figure out flags. We can then
get rid of the 'myflags' parameter to various functions, and instead
refer to client for everything we need (we still have to perform a
bitwise-OR for NBD_FLAG_SEND_DF during NBD_OPT_EXPORT_NAME and
NBD_OPT_EXPORT_GO, but it's easier to see what is being computed).
This lets us quit advertising senseless flags for read-only images, as
well as making the next patch for exposing FAST_ZERO support easier to
write.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-2-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: improve commit message, update iotest 223]
Thanks to our recent move to use glib's g_autofree, I can join the
bandwagon. Getting rid of gotos is fun ;)
There are probably more places where we could register cleanup
functions and get rid of more gotos; this patch just focuses on the
labels that existed merely to call g_free.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190824172813.29720-2-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
The NBD specification defines NBD_FLAG_CAN_MULTI_CONN, which can be
advertised when the server promises cache consistency between
simultaneous clients (basically, rules that determine what FUA and
flush from one client are able to guarantee for reads from another
client). When we don't permit simultaneous clients (such as qemu-nbd
without -e), the bit makes no sense; and for writable images, we
probably have a lot more work before we can declare that actions from
one client are cache-consistent with actions from another. But for
read-only images, where flush isn't changing any data, we might as
well advertise multi-conn support. What's more, advertisement of the
bit makes it easier for clients to determine if 'qemu-nbd -e' was in
use, where a second connection will succeed rather than hang until the
first client goes away.
This patch affects qemu as server in advertising the bit. We may want
to consider patches to qemu as client to attempt parallel connections
for higher throughput by spreading the load over those connections
when a server advertises multi-conn, but for now sticking to one
connection per nbd:// BDS is okay.
See also: https://bugzilla.redhat.com/1708300
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190815185024.7010-1-eblake@redhat.com>
[eblake: tweak blockdev-nbd.c to not request shared when writable,
fix iotest 233]
Reviewed-by: John Snow <jsnow@redhat.com>
Add a public interface for get. While we're at it,
rename "bdrv_get_dirty_bitmap_locked" to "bdrv_dirty_bitmap_get_locked".
(There are more functions to rename to the bdrv_dirty_bitmap_VERB form,
but they will wait until the conclusion of this series.)
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-11-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190812052359.30071-20-armbru@redhat.com>
