From: Dmitry Antipov <dmantipov@yandex.ru>
Date: Mon, 13 Oct 2025 06:28:26 +0000 (+0300)
Subject: ocfs2: add boundary check to ocfs2_check_dir_entry()
X-Git-Tag: v6.19-rc1~70^2~115
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=390ac56cf0f687de53695648bc6f2259a7eae429;p=thirdparty%2Fkernel%2Flinux.git

ocfs2: add boundary check to ocfs2_check_dir_entry()

In 'ocfs2_check_dir_entry()', add extra check whether at least the
smallest possible dirent may be located at the specified offset within
bh's data, thus preventing an out-of-bounds accesses below.

Link: https://lkml.kernel.org/r/20251013062826.122586-1-dmantipov@yandex.ru
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reported-by: syzbot+b20bbf680bb0f2ecedae@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b20bbf680bb0f2ecedae
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Joseph Qi <jiangqi903@gmail.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index dc3d66263335d..2785ff245e79e 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -302,8 +302,21 @@ static int ocfs2_check_dir_entry(struct inode *dir,
 				 unsigned long offset)
 {
 	const char *error_msg = NULL;
-	const int rlen = le16_to_cpu(de->rec_len);
-	const unsigned long next_offset = ((char *) de - buf) + rlen;
+	unsigned long next_offset;
+	int rlen;
+
+	if (offset > size - OCFS2_DIR_REC_LEN(1)) {
+		/* Dirent is (maybe partially) beyond the buffer
+		 * boundaries so touching 'de' members is unsafe.
+		 */
+		mlog(ML_ERROR, "directory entry (#%llu: offset=%lu) "
+		     "too close to end or out-of-bounds",
+		     (unsigned long long)OCFS2_I(dir)->ip_blkno, offset);
+		return 0;
+	}
+
+	rlen = le16_to_cpu(de->rec_len);
+	next_offset = ((char *) de - buf) + rlen;
 
 	if (unlikely(rlen < OCFS2_DIR_REC_LEN(1)))
 		error_msg = "rec_len is smaller than minimal";