[04/13] xfs_scrub: avoid potential UAF after freeing a duplicate name entry

Commit Message

Darrick J. Wong Dec. 31, 2023, 10:46 p.m. UTC

From: Darrick J. Wong <[e-mail]>

Change the function declaration of unicrash_add to set the caller's
@new_entry to NULL if we detect an updated name entry and do not wish to
continue processing.  This avoids a theoretical UAF if the unicrash_add
caller were to accidentally continue using the pointer.

This isn't an /actual/ UAF because the function formerly set @badflags
to zero, but let's be a little defensive.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 scrub/unicrash.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Patch

diff --git a/scrub/unicrash.c b/scrub/unicrash.c
index fc1adb2caab..5a61d69705b 100644
--- a/scrub/unicrash.c
+++ b/scrub/unicrash.c
@@ -626,10 +626,11 @@  _("Unicode name \"%s\" in %s could be confused with \"%s\"."),
 static void
 unicrash_add(
 	struct unicrash		*uc,
-	struct name_entry	*new_entry,
+	struct name_entry	**new_entryp,
 	unsigned int		*badflags,
 	struct name_entry	**existing_entry)
 {
+	struct name_entry	*new_entry = *new_entryp;
 	struct name_entry	*entry;
 	size_t			bucket;
 	xfs_dahash_t		hash;
@@ -652,7 +653,7 @@  unicrash_add(
 			entry->ino = new_entry->ino;
 			uc->buckets[bucket] = new_entry->next;
 			name_entry_free(new_entry);
-			*badflags = 0;
+			*new_entryp = NULL;
 			return;
 		}
 
@@ -695,8 +696,8 @@  __unicrash_check_name(
 		return 0;
 
 	name_entry_examine(new_entry, &badflags);
-	unicrash_add(uc, new_entry, &badflags, &dup_entry);
-	if (badflags)
+	unicrash_add(uc, &new_entry, &badflags, &dup_entry);
+	if (new_entry && badflags)
 		unicrash_complain(uc, dsc, namedescr, new_entry, badflags,
 				dup_entry);