diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2023-11-20 20:02:11 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2023-11-25 02:54:14 -0500 |
| commit | a8b0026847b8c43445c921ad2c85521c92eb175f (patch) | |
| tree | 39078ede8594fab57ee0486e522655df86cb131f /fs/nfsd | |
| parent | dbd4540df2b2857a91593754275c02f3e415fc30 (diff) | |
rename(): avoid a deadlock in the case of parents having no common ancestor
... and fix the directory locking documentation and proof of correctness.
Holding ->s_vfs_rename_mutex *almost* prevents ->d_parent changes; the
case where we really don't want it is splicing the root of disconnected
tree to somewhere.
In other words, ->s_vfs_rename_mutex is sufficient to stabilize "X is an
ancestor of Y" only if X and Y are already in the same tree. Otherwise
it can go from false to true, and one can construct a deadlock on that.
Make lock_two_directories() report an error in such case and update the
callers of lock_rename()/lock_rename_child() to handle such errors.
And yes, such conditions are not impossible to create ;-/
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/nfsd')
| -rw-r--r-- | fs/nfsd/vfs.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index fbbea7498f02..a99260c3f9bc 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1813,6 +1813,10 @@ retry: } trap = lock_rename(tdentry, fdentry); + if (IS_ERR(trap)) { + err = (rqstp->rq_vers == 2) ? nfserr_acces : nfserr_xdev; + goto out; + } err = fh_fill_pre_attrs(ffhp); if (err != nfs_ok) goto out_unlock; |