From: Mike Snitzer <snitzer@kernel.org>
To: Jens Axboe <axboe@kernel.dk>, Mikulas Patocka <mpatocka@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Christoph Hellwig <hch@lst.de>,
"Darrick J. Wong" <djwong@kernel.org>,
dm-devel@redhat.com, linux-block@vger.kernel.org
Subject: Re: block: fix a crash when bio_for_each_folio_all iterates over an empty bio
Date: Tue, 18 Apr 2023 11:20:33 -0400 [thread overview]
Message-ID: <ZD61QWC6TW59anIM@redhat.com> (raw)
In-Reply-To: <alpine.LRH.2.21.2304171433370.17217@file01.intranet.prod.int.rdu2.redhat.com>
On Mon, Apr 17 2023 at 3:11P -0400,
Mikulas Patocka <mpatocka@redhat.com> wrote:
> If we use bio_for_each_folio_all on an empty bio, it will access the first
> bio vector unconditionally (it is uninitialized) and it may crash
> depending on the uninitialized data.
>
> This patch fixes it by checking the parameter "i" against "bio->bi_vcnt"
> and returning NULL fi->folio if it is out of range.
>
> The patch also drops the test "if (fi->_i + 1 < bio->bi_vcnt)" from
> bio_next_folio because the same condition is already being checked in
> bio_first_folio.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This fix is a prereq for this dm-crypt patch to use folios:
https://patchwork.kernel.org/project/dm-devel/patch/alpine.LRH.2.21.2302161619430.5436@file01.intranet.prod.int.rdu2.redhat.com/
Mikulas explained why an empty bio is possible here:
https://listman.redhat.com/archives/dm-devel/2023-April/053916.html
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
next prev parent reply other threads:[~2023-04-18 15:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-17 19:11 [PATCH] block: fix a crash when bio_for_each_folio_all iterates over an empty bio Mikulas Patocka
2023-04-17 19:32 ` Matthew Wilcox
2023-04-17 19:56 ` Mikulas Patocka
2023-04-18 4:57 ` Christoph Hellwig
2023-04-18 15:20 ` Mike Snitzer [this message]
2023-06-09 13:22 ` Mike Snitzer
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