linux-kernel - Re: [PATCH] bcachefs: Fix oob in bch2_dev_journal

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Message-ID: <m5tgdpvt4bzaikdmhlxzwrceww5vh5b237qesdosf6nn4hyhan@4brk2v5w26u4>
Date: Mon, 19 Aug 2024 03:05:33 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: syzbot+47ecc948aadfb2ab3efc@...kaller.appspotmail.com, 
	linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] bcachefs: Fix oob in bch2_dev_journal_init

On Mon, Aug 19, 2024 at 02:47:54PM GMT, Lizhi Xu wrote:
> When journal v2 entry nr overflow, it will cause the value of ja->nr to
> be incorrect, this will result in the allocated memory to ja->buckets
> being too small, leading to out of bounds access.
> 
> Reported-by: syzbot+47ecc948aadfb2ab3efc@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=47ecc948aadfb2ab3efc
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> ---
>  fs/bcachefs/journal.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
> index 13669dd0e375..d4fb5a23b3f6 100644
> --- a/fs/bcachefs/journal.c
> +++ b/fs/bcachefs/journal.c
> @@ -1307,8 +1307,18 @@ int bch2_dev_journal_init(struct bch_dev *ca, struct bch_sb *sb)
>  	if (journal_buckets_v2) {
>  		unsigned nr = bch2_sb_field_journal_v2_nr_entries(journal_buckets_v2);
>  
> -		for (unsigned i = 0; i < nr; i++)
> +		for (unsigned i = 0; i < nr; i++) {
>  			ja->nr += le64_to_cpu(journal_buckets_v2->d[i].nr);
> +			if (le64_to_cpu(journal_buckets_v2->d[i].nr) > UINT_MAX) {
> +				struct bch_fs *c = ca->fs;
> +				struct printbuf buf = PRINTBUF;
> +				prt_printf(&buf, "journal v2 entry d[%u].nr %lu overflow!\n", i,
> +					le64_to_cpu(journal_buckets_v2->d[i].nr));
> +				bch_info(c, "%s", buf.buf);
> +				printbuf_exit(&buf);
> +				return -BCH_ERR_ENOMEM_dev_journal_init;
> +			}
> +		}

this should be done in the validation code