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9p: take write lock on fid path updates (CVE-2018-19364)

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Recent commit 5b76ef50f6 fixed a race where v9fs_co_open2() could
possibly overwrite a fid path with v9fs_path_copy() while it is being
accessed by some other thread, ie, use-after-free that can be detected
by ASAN with a custom 9p client.

It turns out that the same can happen at several locations where
v9fs_path_copy() is used to set the fid path. The fix is again to
take the write lock.

Fixes CVE-2018-19364.

Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
This commit is contained in:
Greg Kurz 2018-11-20 13:00:35 +01:00
parent 3c035a41dc
commit 5b3c77aa58
1 changed files with 15 additions and 0 deletions
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15
hw/9pfs/9p.c
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@ -1391,7 +1391,9 @@ static void coroutine_fn v9fs_walk(void *opaque)
err = -EINVAL;
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
} else {
newfidp = alloc_fid(s, newfid);
if (newfidp == NULL) {
@ -2160,6 +2162,7 @@ static void coroutine_fn v9fs_create(void *opaque)
V9fsString extension;
int iounit;
V9fsPDU *pdu = opaque;
V9fsState *s = pdu->s;
v9fs_path_init(&path);
v9fs_string_init(&name);
@ -2200,7 +2203,9 @@ static void coroutine_fn v9fs_create(void *opaque)
if (err < 0) {
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
err = v9fs_co_opendir(pdu, fidp);
if (err < 0) {
goto out;
@ -2216,7 +2221,9 @@ static void coroutine_fn v9fs_create(void *opaque)
if (err < 0) {
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
} else if (perm & P9_STAT_MODE_LINK) {
int32_t ofid = atoi(extension.data);
V9fsFidState *ofidp = get_fid(pdu, ofid);
@ -2234,7 +2241,9 @@ static void coroutine_fn v9fs_create(void *opaque)
fidp->fid_type = P9_FID_NONE;
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
err = v9fs_co_lstat(pdu, &fidp->path, &stbuf);
if (err < 0) {
fidp->fid_type = P9_FID_NONE;
@ -2272,7 +2281,9 @@ static void coroutine_fn v9fs_create(void *opaque)
if (err < 0) {
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
} else if (perm & P9_STAT_MODE_NAMED_PIPE) {
err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,
0, S_IFIFO | (perm & 0777), &stbuf);
@ -2283,7 +2294,9 @@ static void coroutine_fn v9fs_create(void *opaque)
if (err < 0) {
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
} else if (perm & P9_STAT_MODE_SOCKET) {
err = v9fs_co_mknod(pdu, fidp, &name, fidp->uid, -1,
0, S_IFSOCK | (perm & 0777), &stbuf);
@ -2294,7 +2307,9 @@ static void coroutine_fn v9fs_create(void *opaque)
if (err < 0) {
goto out;
}
v9fs_path_write_lock(s);
v9fs_path_copy(&fidp->path, &path);
v9fs_path_unlock(s);
} else {
err = v9fs_co_open2(pdu, fidp, &name, -1,
omode_to_uflags(mode)|O_CREAT, perm, &stbuf);