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Thu, 06 Aug 2026 05:21:40 -0700 (PDT) From: Zhan Xusheng X-Google-Original-From: Zhan Xusheng To: Joseph Qi , Andrew Morton Cc: Mark Fasheh , Joel Becker , ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, zhanxusheng@xiaomi.com Subject: [PATCH] ocfs2: bound-check dir entries in the readdir re-validation scan Date: Thu, 6 Aug 2026 20:21:33 +0800 Message-ID: <20260806122133.956847-1-zhanxusheng@xiaomi.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 =3D 0; i < sb->s_blocksize && i < offset; ) { de =3D (struct ocfs2_dir_entry *)(bh->b_data + i); if (le16_to_cpu(de->rec_len) < OCFS2_DIR_REC_LEN(1)) break; i +=3D 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. Suggested-by: Joseph Qi Fixes: ccd979bdbce9 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem") Cc: stable@vger.kernel.org Link: https://sashiko.dev/#/patchset/20260806022044.167962-1-zhanxusheng@xi= aomi.com Signed-off-by: Zhan Xusheng --- fs/ocfs2/dir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c index d7fc3cccf2f4..3b606b4c04dd 100644 --- a/fs/ocfs2/dir.c +++ b/fs/ocfs2/dir.c @@ -1903,7 +1903,8 @@ static int ocfs2_dir_foreach_blk_el(struct inode *ino= de, * dirent right now. Scan from the start of the block * to make sure. */ if (!inode_eq_iversion(inode, *f_version)) { - for (i =3D 0; i < sb->s_blocksize && i < offset; ) { + for (i =3D 0; i + OCFS2_DIR_REC_LEN(1) <=3D sb->s_blocksize && + i < offset;) { de =3D (struct ocfs2_dir_entry *) (bh->b_data + i); /* It's too expensive to do a full * dirent test each time round this --=20 2.43.0