linux-kernel - Re: [PATCH v2] ocfs2: Fix shift-out-of-bounds UBSAN bug in ocfs2_verify

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Message-ID: <021886f3-a1fd-4de3-a97c-9320009ca29e@linux.alibaba.com>
Date: Tue, 20 Aug 2024 09:27:49 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: qasdev <qasdev00@...il.com>, mark@...heh.com, jlbec@...lplan.org,
 akpm <akpm@...ux-foundation.org>
Cc: ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ocfs2: Fix shift-out-of-bounds UBSAN bug in
 ocfs2_verify_volume()



On 8/20/24 9:22 AM, qasdev wrote:
> This patch addresses a shift-out-of-bounds error in the
> ocfs2_verify_volume() function, identified by UBSAN. The bug was triggered
> by an invalid s_clustersize_bits value (e.g., 1548), which caused the
> expression "1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits)"
> to exceed the limits of a 32-bit integer,
> leading to an out-of-bounds shift.
> 
> Reported-by: syzbot <syzbot+f3fff775402751ebb471@...kaller.appspotmail.com>
> Closes: https://syzkaller.appspot.com/bug?extid=f3fff775402751ebb471
> Tested-by: syzbot <syzbot+f3fff775402751ebb471@...kaller.appspotmail.com>
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>

Looks fine.
Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
> ---
>  fs/ocfs2/super.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> index afee70125ae3..b704983b2112 100644
> --- a/fs/ocfs2/super.c
> +++ b/fs/ocfs2/super.c
> @@ -2357,8 +2357,8 @@ static int ocfs2_verify_volume(struct ocfs2_dinode *di,
>  			     (unsigned long long)bh->b_blocknr);
>  		} else if (le32_to_cpu(di->id2.i_super.s_clustersize_bits) < 12 ||
>  			    le32_to_cpu(di->id2.i_super.s_clustersize_bits) > 20) {
> -			mlog(ML_ERROR, "bad cluster size found: %u\n",
> -			     1 << le32_to_cpu(di->id2.i_super.s_clustersize_bits));
> +			mlog(ML_ERROR, "bad cluster size bit found: %u\n",
> +			     le32_to_cpu(di->id2.i_super.s_clustersize_bits));
>  		} else if (!le64_to_cpu(di->id2.i_super.s_root_blkno)) {
>  			mlog(ML_ERROR, "bad root_blkno: 0\n");
>  		} else if (!le64_to_cpu(di->id2.i_super.s_system_dir_blkno)) {