When reading an inode from disk, ocfs2_validate_inode_block() performs
various sanity checks but does not validate the size of inline
directories. If the filesystem is corrupted, an inline directory'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 inline directories have i_size <= id_count. This catches the
corruption early during inode read and prevents all downstream code
from operating on invalid data.

Reported-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/ocfs2/inode.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 8340525e5589..9eb364bef5c3 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1521,6 +1520,20 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		}
 	}
 
+	if (S_ISDIR(le16_to_cpu(di->i_mode)) &&
+	    (di->i_dyn_features & cpu_to_le16(OCFS2_INLINE_DATA_FL))) {
+		struct ocfs2_inline_data *data = &di->id2.i_data;
+
+		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
+			rc = ocfs2_error(sb,
+					 "Invalid dinode #%llu: inline directory 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;
+		}
+	}
+
 	rc = 0;
 
 bail:
-- 
2.43.0

On Thu, Dec 11, 2025 at 05:22:31PM +0530, Deepanshu Kartikey wrote:
> When reading an inode from disk, ocfs2_validate_inode_block() performs
> various sanity checks but does not validate the size of inline
> directories. If the filesystem is corrupted, an inline directory'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 inline directories have i_size <= id_count. This catches the
> corruption early during inode read and prevents all downstream code
> from operating on invalid data.
> 
> Reported-by: syzbot+c897823f699449cc3eb4@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c897823f699449cc3eb4
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
>  fs/ocfs2/inode.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index 8340525e5589..9eb364bef5c3 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1521,6 +1520,20 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		}
>  	}
>  
> +	if (S_ISDIR(le16_to_cpu(di->i_mode)) &&

The S_ISDIR() looks useless, OCFS2_INLINE_DATA_FL is used for both DIR and
REG.

> +	    (di->i_dyn_features & cpu_to_le16(OCFS2_INLINE_DATA_FL))) {

Above line is enough to handle this case.

> +		struct ocfs2_inline_data *data = &di->id2.i_data;
> +
> +		if (le64_to_cpu(di->i_size) > le16_to_cpu(data->id_count)) {
> +			rc = ocfs2_error(sb,
> +					 "Invalid dinode #%llu: inline directory i_size %llu exceeds id_count %u\n",

Please run "kernel/scripts/checkpatch.pl" on this patch.

Thanks,
Heming
> +					 (unsigned long long)bh->b_blocknr,
> +					 (unsigned long long)le64_to_cpu(di->i_size),
> +					 le16_to_cpu(data->id_count));
> +			goto bail;
> +		}
> +	}
> +
>  	rc = 0;
>  
>  bail:
> -- 
> 2.43.0
> 
>