linux-kernel - Re: [PATCH v3] ocfs2: validate i_blkno and BITMAP_FL consistency in ocfs2_validate_inode

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Message-ID: <95b86635-8ab4-4b40-9eec-2610b65150b2@linux.alibaba.com>
Date: Mon, 26 Jan 2026 11:34:24 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Deepanshu Kartikey <kartikey406@...il.com>
Cc: ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org,
 syzbot+44c564a3cb08605f34a1@...kaller.appspotmail.com,
 Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>,
 Heming Zhao <heming.zhao@...e.com>
Subject: Re: [PATCH v3] ocfs2: validate i_blkno and BITMAP_FL consistency in
 ocfs2_validate_inode_block



On 1/24/26 1:01 PM, Deepanshu Kartikey wrote:
> ocfs2_is_cluster_bitmap() checks whether an inode is the global bitmap
> by comparing ip_blkno with osb->bitmap_blkno. A corrupted filesystem
> can have an inode with i_blkno and OCFS2_BITMAP_FL flag inconsistent:
> - i_blkno matches bitmap_blkno but BITMAP_FL is not set, or
> - BITMAP_FL is set but i_blkno does not match bitmap_blkno
> 
> In either case, ocfs2_is_cluster_bitmap() returns incorrect results,
> triggering BUG_ON in ocfs2_block_group_search() or
> ocfs2_cluster_group_search() causing a kernel panic.
> 
> Call trace:
>   ocfs2_block_group_search+0x1c7/0x2c0 fs/ocfs2/suballoc.c:1611
>   ocfs2_search_chain+0x38a/0x1010 fs/ocfs2/suballoc.c:1764
>   ocfs2_claim_suballoc_bits+0x3a4/0x650 fs/ocfs2/suballoc.c:1978
>   ocfs2_claim_new_inode+0x95/0x130 fs/ocfs2/suballoc.c:2137
>   ocfs2_mknod_locked+0x129/0x510 fs/ocfs2/namei.c:568
>   ocfs2_mknod+0x5c7/0x11d0 fs/ocfs2/namei.c:802
>   ocfs2_create+0x136/0x170 fs/ocfs2/namei.c:852
> 
> Add validation in ocfs2_validate_inode_block() to check that i_blkno
> and OCFS2_BITMAP_FL are consistent:
> - If i_blkno matches bitmap_blkno, BITMAP_FL must be set
> - If BITMAP_FL is set, i_blkno must match bitmap_blkno
> 
> This catches corrupted inodes early when reading from disk.
> 
> Reported-by: syzbot+44c564a3cb08605f34a1@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=44c564a3cb08605f34a1
> Tested-by: syzbot+44c564a3cb08605f34a1@...kaller.appspotmail.com
> Link: https://lore.kernel.org/all/20260104014028.305029-1-kartikey406@gmail.com/T/ [v1]
> Link: https://lore.kernel.org/all/20260110054443.604944-1-kartikey406@gmail.com/T/ [v2]
> Signed-off-by: Deepanshu Kartikey <kartikey406@...il.com>
> ---
> v3:
>   - Move validation to ocfs2_validate_inode_block() to catch corruption
>     early when inode is read from disk (Joseph Qi)
>   - Add check for both directions of inconsistency
> 
> v2:
>   - Fix commit message - ocfs2_is_cluster_bitmap() checks ip_blkno
>     against bitmap_blkno, not a flag (Joseph Qi)
> ---
>  fs/ocfs2/inode.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> index b5fcc2725a29..2d80934d14b4 100644
> --- a/fs/ocfs2/inode.c
> +++ b/fs/ocfs2/inode.c
> @@ -1529,6 +1529,27 @@ int ocfs2_validate_inode_block(struct super_block *sb,
>  		}
>  	}
>  
> +	/*
> +	 * Validate bitmap flag consistency with bitmap_blkno.
> +	 * A corrupted inode with mismatched i_blkno and BITMAP_FL would
> +	 * cause ocfs2_is_cluster_bitmap() to return incorrect results,
> +	 * triggering BUG_ON in ocfs2_block_group_search() or
> +	 * ocfs2_cluster_group_search().
> +	 */
> +	if (le64_to_cpu(di->i_blkno) == OCFS2_SB(sb)->bitmap_blkno &&
> +	    !(di->i_flags & cpu_to_le32(OCFS2_BITMAP_FL))) {
> +		rc = ocfs2_error(sb,
> +				 "Invalid dinode #%llu: i_blkno matches bitmap but BITMAP flag not set\n",
> +				 (unsigned long long)bh->b_blocknr);
> +		goto bail;
> +	} else if (di->i_flags & cpu_to_le32(OCFS2_BITMAP_FL) &&
> +		   le64_to_cpu(di->i_blkno) != OCFS2_SB(sb)->bitmap_blkno) {

Ummm... This is not right.
OCFS2_BITMAP_FL is set not only for global bitmap, but also for
localalloc, extent alloc, inode alloc, etc.
BTW, OCFS2_BITMAP_FL should be checked along with OCFS2_CHAIN_FL.

Thanks,
Joseph

> +		rc = ocfs2_error(sb,
> +				 "Invalid dinode #%llu: BITMAP flag set but i_blkno does not match bitmap\n",
> +				 (unsigned long long)bh->b_blocknr);
> +		goto bail;
> +	}
> +
>  	rc = 0;
>  
>  bail: