[PATCH v2] ufs: free the buffer head container in ubh_bforget

[Ali Ahmet Memis <ali@iusegentoo.com>]

ubh_bforget() forgets the buffer heads referenced by a struct
ufs_buffer_head but never frees the container itself, unlike its sibling
ubh_brelse() which calls kfree() on the way out. The only caller,
free_full_branch(), allocates the container through ubh_bread() while
releasing an indirect block during truncate, so every fully removed
indirect block leaks one ufs_buffer_head. Truncating or unlinking a
large file then leaks one allocation per indirect block, which kmemleak
reports with a free_full_branch, ufs_truncate_blocks, ufs_evict_inode
backtrace.

Free the container after forgetting its buffers, mirroring ubh_brelse().
Drop the NULL test in the loop as well, which Luis already noted is
redundant because bforget() ignores a NULL buffer head; ubh_brelse() has
no such test either, so the two now match.

Luis Henriques posted this fix in 2018. It never got a single reply and
was never applied, while fs/ufs had no active maintainer, and the leak is
still present.

Link: https://lore.kernel.org/all/20180705150415.25070-1-lhenriques@suse.com/
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
---
v2: drop the NULL test in the loop, as Luis pointed out. That makes this
    the same change as his 2018 patch; if you would rather it went in
    under his authorship I am happy to resend it that way, his call.
    Whitespace on the touched lines modernised to keep checkpatch quiet.

v1: https://lore.kernel.org/all/20260801024119.12667-1-ali@iusegentoo.com/

 fs/ufs/util.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ufs/util.c b/fs/ufs/util.c
index dff6f74618de..603d80b93066 100644
--- a/fs/ufs/util.c
+++ b/fs/ufs/util.c
@@ -117,8 +117,9 @@ void ubh_bforget (struct ufs_buffer_head * ubh)
 	unsigned i;
 	if (!ubh) 
 		return;
-	for ( i = 0; i < ubh->count; i++ ) if ( ubh->bh[i] ) 
-		bforget (ubh->bh[i]);
+	for (i = 0; i < ubh->count; i++)
+		bforget(ubh->bh[i]);
+	kfree(ubh);
 }
  
 int ubh_buffer_dirty (struct ufs_buffer_head * ubh)

base-commit: 2d2338c93da79b3bfe4b6099a931d9468d539952
-- 
2.55.0