ocfs2: validate inline data i_size during inode read

When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline data.  If
the filesystem is corrupted, an inode's i_size can exceed the actual
inline data capacity (id_count).

This causes ocfs2_dir_foreach_blk_id() to iterate beyond the inline data
buffer, triggering a use-after-free when accessing directory entries from
freed memory.

In the syzbot report:
  - i_size was 1099511627576 bytes (~1TB)
  - Actual inline data capacity (id_count) is typically <256 bytes
  - A garbage rec_len (54648) caused ctx->pos to jump out of bounds
  - This triggered a UAF in ocfs2_check_dir_entry()

Fix by adding a validation check in ocfs2_validate_inode_block() to ensure
inodes with inline data have i_size <= id_count.  This catches the
corruption early during inode read and prevents all downstream code from
operating on invalid data.

Link: https://lkml.kernel.org/r/20251212052132.16750-1-kartikey406@gmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Tested-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/20251211115231.3560028-1-kartikey406@gmail.com/T/
Link: https://lore.kernel.org/all/20251212040400.6377-1-kartikey406@gmail.com/T/
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>

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index c95c998811ae54d1289a2bb0179a267df68f0307..03a51662ea8e79f7a64fcd320b974f954b2ea8bf 100644 (file)
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1494,12 +1494,25 @@ int ocfs2_validate_inode_block(struct super_block *sb,
                goto bail;
        }
 
-       if ((le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) &&
-           le32_to_cpu(di->i_clusters)) {
-               rc = ocfs2_error(sb, "Invalid dinode %llu: %u clusters\n",
-                                (unsigned long long)bh->b_blocknr,
-                                le32_to_cpu(di->i_clusters));
-               goto bail;
+       if (le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) {
+               struct ocfs2_inline_data *data = &di->id2.i_data;
+
+               if (le32_to_cpu(di->i_clusters)) {
+                       rc = ocfs2_error(sb,
+                                        "Invalid dinode %llu: %u clusters\n",
+                                        (unsigned long long)bh->b_blocknr,
+                                        le32_to_cpu(di->i_clusters));
+                       goto bail;
+               }
+
+               if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
+                       rc = ocfs2_error(sb,
+                                        "Invalid dinode #%llu: inline data i_size %llu exceeds id_count %u\n",
+                                        (unsigned long long)bh->b_blocknr,
+                                        (unsigned long long)le64_to_cpu(di->i_size),
+                                        le16_to_cpu(data->id_count));
+                       goto bail;
+               }
        }
 
        if (le32_to_cpu(di->i_flags) & OCFS2_CHAIN_FL) {