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cache: fix vexec panic when racing against vgone

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Use of dead_vnodeops would result in a panic instead of returning the intended
EOPNOTSUPP error.

While here make sure to abort, not just try to return a partial result.
The former allows the regular lookup to restart from scratch, while the latter
makes it stuck with an unusable vnode.

Reported by:	kevans
This commit is contained in:
Mateusz Guzik 2020-10-09 19:10:00 +00:00
parent b56d7f9663
commit eb88fed446
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=366582
2 changed files with 25 additions and 10 deletions
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1
sys/fs/deadfs/dead_vnops.c
View file

@ -79,6 +79,7 @@ struct vop_vector dead_vnodeops = {
.vop_vptocnp = VOP_EBADF,
.vop_unset_text = dead_unset_text,
.vop_write = dead_write,
.vop_fplookup_vexec = VOP_EOPNOTSUPP,
};
VFS_VOP_VECTOR_REGISTER(dead_vnodeops);

34
sys/kern/vfs_cache.c
View file

@ -4040,32 +4040,46 @@ cache_fplookup_parse_advance(struct cache_fpl *fpl)
}
}
/*
* See the API contract for VOP_FPLOOKUP_VEXEC.
*/
static int __noinline
cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
{
struct vnode *dvp;
seqc_t dvp_seqc;
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
/*
* Hack: they may be looking up foo/bar, where foo is a
* regular file. In such a case we need to turn ENOTDIR,
* but we may happen to get here with a different error.
*/
if (fpl->dvp->v_type != VDIR) {
if (dvp->v_type != VDIR) {
/*
* The check here is predominantly to catch
* EOPNOTSUPP from dead_vnodeops. If the vnode
* gets doomed past this point it is going to
* fail seqc verification.
*/
if (VN_IS_DOOMED(dvp)) {
return (cache_fpl_aborted(fpl));
}
error = ENOTDIR;
}
switch (error) {
case EAGAIN:
/*
* Can happen when racing against vgone.
* */
case EOPNOTSUPP:
cache_fpl_partial(fpl);
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
error = cache_fpl_aborted(fpl);
} else {
cache_fpl_partial(fpl);
}
break;
default:
/*
* See the API contract for VOP_FPLOOKUP_VEXEC.
*/
if (!vn_seqc_consistent(fpl->dvp, fpl->dvp_seqc)) {
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
error = cache_fpl_aborted(fpl);
} else {
cache_fpl_smr_exit(fpl);