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From:   Andreas Gruenbacher <agruenba@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Junichi Nomura <j-nomura@ce.jp.nec.com>,
        Christoph Hellwig <hch@lst.de>, Ming Lei <ming.lei@redhat.com>,
        Hannes Reinecke <hare@suse.de>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Andreas Gruenbacher <agruenba@redhat.com>,
        stable@vger.kernel.org
Subject: [PATCH] block: fix "check bi_size overflow before merge"
Date:   Mon,  9 Dec 2019 20:11:14 +0100
Message-Id: <20191209191114.17266-1-agruenba@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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This partially reverts commit e3a5d8e386c3fb973fa75f2403622a8f3640ec06.

Commit e3a5d8e386c3 ("check bi_size overflow before merge") adds a bio_full
check to __bio_try_merge_page.  This will cause __bio_try_merge_page to fai=
l
when the last bi_io_vec has been reached.  Instead, what we want here is on=
ly
the bi_size overflow check.

Fixes: e3a5d8e386c3 ("block: check bi_size overflow before merge")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 block/bio.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 9d54aa37ce6c..a5d75f6bf4c7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -754,10 +754,12 @@ bool __bio_try_merge_page(struct bio *bio, struct pag=
e *page,
 =09if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 =09=09return false;
=20
-=09if (bio->bi_vcnt > 0 && !bio_full(bio, len)) {
+=09if (bio->bi_vcnt > 0) {
 =09=09struct bio_vec *bv =3D &bio->bi_io_vec[bio->bi_vcnt - 1];
=20
 =09=09if (page_is_mergeable(bv, page, len, off, same_page)) {
+=09=09=09if (bio->bi_iter.bi_size > UINT_MAX - len)
+=09=09=09=09return false;
 =09=09=09bv->bv_len +=3D len;
 =09=09=09bio->bi_iter.bi_size +=3D len;
 =09=09=09return true;
--=20
2.20.1