From: Michael Bommarito <michael.bommarito@gmail.com> mainline inclusion from mainline-v7.3-rc1 commit 526c49cff3f72c3ec74752016380c7567040581b category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18850 CVE: CVE-2026-89485 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- nlm_traverse_files() pins the current file with f_count++ across a mutex_unlock for nlm_inspect_file(), but nothing pins the saved next pointer. A concurrent nlm_release_file() can kfree the next file during the unlock window, and the iterator dereferences freed memory on the next loop step. Pin both current and next before the lock-drop. Advance by swapping the pinned cursors at the end of each iteration so next is always held alive across the unlock. Always call nlm_file_release() after dropping the iteration pin, regardless of whether the file matched the predicate. Use nlm_file_inuse(), which does a live walk of the inode lock list, rather than the cached f_locks field, so skipped files that never ran nlm_inspect_file() are evaluated correctly. Because every file in a hash bucket is now pinned and released, files skipped by the is_failover_file predicate that have no locks, blocks, shares, or external references are deleted during traversal. The old code never evaluated skipped files for cleanup. The new behavior is intentional: such files are stale and should not persist in the table. Fixes: 01df9c5e918a ("LOCKD: Fix a deadlock in nlm_traverse_files()") Cc: stable@vger.kernel.org Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com> Link: https://patch.msgid.link/20260524115527.1734251-1-michael.bommarito@gmail.co... Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Conflicts: fs/lockd/svcsubs.c [Downstream tree has no standalone nlm_close_files() helper; the teardown was inlined inside nlm_traverse_files(). Add nlm_file_release() (as upstream does) and rewrite the traversal loop to the new pinned-cursor form.] Co-authored-by: BackportAgent@deepseek-v4-flash Signed-off-by: Hulk Robot <hulkrobot@huawei.com> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- fs/lockd/svcsubs.c | 52 +++++++++++++++++++++++++++++----------------- 1 file changed, 33 insertions(+), 19 deletions(-) diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c index 028fc152da22..23fd515b2185 100644 --- a/fs/lockd/svcsubs.c +++ b/fs/lockd/svcsubs.c @@ -246,6 +246,11 @@ nlm_file_inuse(struct nlm_file *file) return 0; } +static void nlm_file_release(struct nlm_file *file) +{ + if (!nlm_file_inuse(file)) + nlm_delete_file(file); +} /* * Loop over all files in the file table. */ @@ -253,32 +258,41 @@ static int nlm_traverse_files(void *data, nlm_host_match_fn_t match, int (*is_failover_file)(void *data, struct nlm_file *file)) { - struct hlist_node *next; - struct nlm_file *file; + struct nlm_file *file, *next; int i, ret = 0; mutex_lock(&nlm_file_mutex); for (i = 0; i < FILE_NRHASH; i++) { - hlist_for_each_entry_safe(file, next, &nlm_files[i], f_list) { - if (is_failover_file && !is_failover_file(data, file)) - continue; + file = hlist_entry_safe(nlm_files[i].first, + struct nlm_file, f_list); + if (file) file->f_count++; - mutex_unlock(&nlm_file_mutex); - - /* Traverse locks, blocks and shares of this file - * and update file->f_locks count */ - if (nlm_inspect_file(data, file, match)) - ret = 1; + while (file) { + /* + * Pin the next neighbour before we drop the mutex + * for nlm_inspect_file(); a concurrent + * nlm_release_file() under the same mutex would + * otherwise be free to unlink and kfree it during + * the unlock window, leaving us to dereference a + * freed slab when we walked to next afterwards. + */ + next = hlist_entry_safe(file->f_list.next, + struct nlm_file, f_list); + if (next) + next->f_count++; + + if (!is_failover_file || is_failover_file(data, file)) { + mutex_unlock(&nlm_file_mutex); + + if (nlm_inspect_file(data, file, match)) + ret = 1; + + mutex_lock(&nlm_file_mutex); + } - mutex_lock(&nlm_file_mutex); file->f_count--; - /* No more references to this file. Let go of it. */ - if (list_empty(&file->f_blocks) && !file->f_locks - && !file->f_shares && !file->f_count) { - hlist_del(&file->f_list); - nlmsvc_ops->fclose(file->f_file); - kfree(file); - } + nlm_file_release(file); + file = next; } } mutex_unlock(&nlm_file_mutex); -- 2.34.1