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file-posix: Fix check_hdev_writable() with auto-read-only

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For Linux block devices, being able to open the device read-write
doesn't necessarily mean that the device is actually writable (one
example is a read-only LV, as you get with lvchange -pr <device>). We
have check_hdev_writable() to check this condition and fail opening the
image read-write if it's not actually writable.

However, this check doesn't take auto-read-only into account, but
results in a hard failure instead of downgrading to read-only where
possible.

Fix this and do the writable check not based on BDRV_O_RDWR, but only
when this actually results in opening the file read-write. A second
check is inserted in raw_reconfigure_getfd() to have the same check when
dynamic auto-read-only upgrades an image file from read-only to
read-write.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200717105426.51134-3-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2020-07-17 12:54:25 +02:00
parent 20eaf1bf6e
commit bca5283bd4
1 changed files with 21 additions and 12 deletions
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33
block/file-posix.c
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@ -425,7 +425,7 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
}
}
static int check_hdev_writable(BDRVRawState *s)
static int check_hdev_writable(int fd)
{
#if defined(BLKROGET)
/* Linux block devices can be configured "read-only" using blockdev(8).
@ -439,7 +439,7 @@ static int check_hdev_writable(BDRVRawState *s)
struct stat st;
int readonly = 0;
if (fstat(s->fd, &st)) {
if (fstat(fd, &st)) {
return -errno;
}
@ -447,7 +447,7 @@ static int check_hdev_writable(BDRVRawState *s)
return 0;
}
if (ioctl(s->fd, BLKROGET, &readonly) < 0) {
if (ioctl(fd, BLKROGET, &readonly) < 0) {
return -errno;
}
@ -642,6 +642,15 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
}
s->fd = fd;
/* Check s->open_flags rather than bdrv_flags due to auto-read-only */
if (s->open_flags & O_RDWR) {
ret = check_hdev_writable(s->fd);
if (ret < 0) {
error_setg_errno(errp, -ret, "The device is not writable");
goto fail;
}
}
s->perm = 0;
s->shared_perm = BLK_PERM_ALL;
@ -1034,6 +1043,15 @@ static int raw_reconfigure_getfd(BlockDriverState *bs, int flags,
}
}
if (fd != -1 && (*open_flags & O_RDWR)) {
ret = check_hdev_writable(fd);
if (ret < 0) {
qemu_close(fd);
error_setg_errno(errp, -ret, "The device is not writable");
return -1;
}
}
return fd;
}
@ -3478,15 +3496,6 @@ hdev_open_Mac_error:
/* Since this does ioctl the device must be already opened */
bs->sg = hdev_is_sg(bs);
if (flags & BDRV_O_RDWR) {
ret = check_hdev_writable(s);
if (ret < 0) {
raw_close(bs);
error_setg_errno(errp, -ret, "The device is not writable");
return ret;
}
}
return ret;
}