+ 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: Tue, 11 Aug 2026 10:43:36 +0800

Patch series "ocfs2: bound-check both readdir re-validation scans", v2.


This patch (of 2):

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);
	}

i walks the block on rec_len values taken from the block itself and the
only thing tested is that rec_len is not too small, so a single bogus
rec_len leaves i anywhere in the block, including its last
OCFS2_DIR_REC_LEN(1) - 1 bytes.  @offset comes from ctx->pos, which
userspace moves with lseek() on the directory fd, and decides how far the
walk gets.

Two bounds are missing, both of which ocfs2_check_dir_entry() applies for
the emit loop below.

de->rec_len sits at byte offset 8 within the entry, so dereferencing de in
that tail reads past the s_blocksize buffer.  ocfs2_check_dir_entry()
declines to look at an entry that close to the end:

	size - buf_offset < OCFS2_DIR_REC_LEN(1)

Nothing bounds i += rec_len either, so i can end up past the block.  The
emit loop that follows is guarded by offset < sb->s_blocksize and does not
run, but

	offset = i;
	ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset;

runs first and ORs a value with bits above the block mask into ctx->pos,
corrupting the block number readdir() resumes from. 
ocfs2_check_dir_entry() rejects that as "directory entry overrun":

	next_offset = buf_offset + rlen;
	... next_offset > size

Apply both bounds.  For a consistent directory this changes nothing:
entries are at least OCFS2_DIR_REC_LEN(1) bytes and do not cross the end
of the block, so no valid entry is skipped.

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

Link: https://lore.kernel.org/20260811024337.3972976-1-zhanxusheng@xiaomi.com
Link: https://sashiko.dev/#/patchset/20260806022044.167962-1-zhanxusheng@xiaomi.com
Link: https://lore.kernel.org/20260811024337.3972976-2-zhanxusheng@xiaomi.com
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-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 |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/ocfs2/dir.c~ocfs2-bound-check-dir-entries-in-the-readdir-re-validation-scan
+++ a/fs/ocfs2/dir.c
@@ -1945,7 +1945,10 @@ 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;) {
+				unsigned int rec_len;
+
 				de = (struct ocfs2_dir_entry *) (bh->b_data + i);
 				/* It's too expensive to do a full
 				 * dirent test each time round this
@@ -1953,10 +1956,11 @@ static int ocfs2_dir_foreach_blk_el(stru
 				 * least that it is non-zero.  A
 				 * failure will be detected in the
 				 * dirent test below. */
-				if (le16_to_cpu(de->rec_len) <
-				    OCFS2_DIR_REC_LEN(1))
+				rec_len = le16_to_cpu(de->rec_len);
+				if (rec_len < OCFS2_DIR_REC_LEN(1) ||
+				    i + rec_len > sb->s_blocksize)
 					break;
-				i += le16_to_cpu(de->rec_len);
+				i += rec_len;
 			}
 			offset = i;
 			ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1))
_

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
ocfs2-bound-check-dir-entries-in-the-inline-data-re-validation-scan.patch