From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Brian Foster <bfoster@redhat.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH] xfs: fix mount failure crash on invalid iclog memory access
Date: Tue, 3 Dec 2019 07:52:56 -0800 [thread overview]
Message-ID: <20191203155256.GI7335@magnolia> (raw)
In-Reply-To: <20191203140524.36043-1-bfoster@redhat.com>
On Tue, Dec 03, 2019 at 09:05:24AM -0500, Brian Foster wrote:
> syzbot (via KASAN) reports a use-after-free in the error path of
> xlog_alloc_log(). Specifically, the iclog freeing loop doesn't
> handle the case of a fully initialized ->l_iclog linked list.
> Instead, it assumes that the list is partially constructed and NULL
> terminated.
>
> This bug manifested because there was no possible error scenario
> after iclog list setup when the original code was added. Subsequent
> code and associated error conditions were added some time later,
> while the original error handling code was never updated. Fix up the
> error loop to terminate either on a NULL iclog or reaching the end
> of the list.
>
> Reported-by: syzbot+c732f8644185de340492@syzkaller.appspotmail.com
> Signed-off-by: Brian Foster <bfoster@redhat.com>
Ahh, a proper S-o-B! Thank you,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
> fs/xfs/xfs_log.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 6a147c63a8a6..f6006d94a581 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1542,6 +1542,8 @@ xlog_alloc_log(
> prev_iclog = iclog->ic_next;
> kmem_free(iclog->ic_data);
> kmem_free(iclog);
> + if (prev_iclog == log->l_iclog)
> + break;
> }
> out_free_log:
> kmem_free(log);
> --
> 2.20.1
>
prev parent reply other threads:[~2019-12-03 15:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-03 14:05 [PATCH] xfs: fix mount failure crash on invalid iclog memory access Brian Foster
2019-12-03 14:09 ` Brian Foster
2019-12-03 15:52 ` Darrick J. Wong [this message]
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