+ ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ocfs2: bound-check dir entries in the readdir re-validation scan
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Zhan Xusheng <zhanxusheng1024@gmail.com>
Subject: ocfs2: bound-check dir entries in the readdir re-validation scan
Date: Thu, 6 Aug 2026 20:21:33 +0800

When the inode version changed since the last readdir(),
ocfs2_dir_foreach_blk_el() re-scans the directory block from its start to
relocate the current position:

	for (i = 0; i < sb->s_blocksize && i < offset; ) {
		de = (struct ocfs2_dir_entry *)(bh->b_data + i);
		if (le16_to_cpu(de->rec_len) < OCFS2_DIR_REC_LEN(1))
			break;
		i += le16_to_cpu(de->rec_len);
	}

The loop dereferences de->rec_len (at byte offset 8 within the entry)
guarded only by i < sb->s_blocksize.  `offset` is derived from ctx->pos,
which userspace controls via lseek() on the directory fd, so i can reach
the last bytes of the block; reading de->rec_len then reads a few bytes
past the s_blocksize-sized block buffer (an out-of-bounds read).

The main emit loop below already guards this via ocfs2_check_dir_entry(),
which rejects entries too close to the buffer end before touching de. 
Apply the same lower bound to the re-validation scan so that a full
minimal directory entry is known to fit before de is dereferenced.  For a
consistent directory this changes nothing: entries are at least
OCFS2_DIR_REC_LEN(1) bytes, so no valid entry starts in the excluded tail.

Found by the sashiko review tool; fix approach suggested by Joseph Qi.

Link: https://lore.kernel.org/20260806122133.956847-1-zhanxusheng@xiaomi.com
Link: https://sashiko.dev/#/patchset/20260806022044.167962-1-zhanxusheng@xiaomi.com
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/dir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ocfs2/dir.c~ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan
+++ a/fs/ocfs2/dir.c
@@ -1945,7 +1945,8 @@ static int ocfs2_dir_foreach_blk_el(stru
 		 * dirent right now.  Scan from the start of the block
 		 * to make sure. */
 		if (!inode_eq_iversion(inode, *f_version)) {
-			for (i = 0; i < sb->s_blocksize && i < offset; ) {
+			for (i = 0; i + OCFS2_DIR_REC_LEN(1) <= sb->s_blocksize &&
+			     i < offset;) {
 				de = (struct ocfs2_dir_entry *) (bh->b_data + i);
 				/* It's too expensive to do a full
 				 * dirent test each time round this
_

Patches currently in -mm which might be from zhanxusheng1024@gmail.com are

maple_tree-remove-unused-mas_is_root_limits.patch
ocfs2-fix-readdir-position-truncation-on-32-bit-kernels.patch
ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan.patch