[dm-devel] [PATCH 5.10 2/2] block: fix bounce_clone_bio for passthrough bios

[Tadeusz Struk]

From: Christoph Hellwig <hch at lst.de>

From: Christoph Hellwig <hch at lst.de>

Upstream commit: b90994c6ab62 ("block: fix bounce_clone_bio for passthrough bios")

This is backport to stable 5.10. It fixes an issue reported by syzbot.
Link: https://syzkaller.appspot.com/bug?id=a3416231e37024a75f2b95bd95db0d8ce8132a84

Now that bio_alloc_bioset does not fall back to kmalloc for a NULL
bio_set, handle that case explicitly and simplify the calling
conventions.

Based on an earlier patch from Chaitanya Kulkarni.

Fixes: 3175199ab0ac ("block: split bio_kmalloc from bio_alloc_bioset")
Reported-by: syzbot+4f441e6ca0fcad141421 at syzkaller.appspotmail.com
Reported-by: Chaitanya Kulkarni <Chaitanya.Kulkarni at wdc.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
Signed-off-by: Tadeusz Struk <tadeusz.struk at linaro.org>
---
 block/bounce.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index 162a6eee8999..4da429de78a2 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -214,8 +214,7 @@ static void bounce_end_io_read_isa(struct bio *bio)
 	__bounce_end_io_read(bio, &isa_page_pool);
 }
 
-static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
-		struct bio_set *bs)
+static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask)
 {
 	struct bvec_iter iter;
 	struct bio_vec bv;
@@ -242,8 +241,11 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 	 *    asking for trouble and would force extra work on
 	 *    __bio_clone_fast() anyways.
 	 */
-
-	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
+	if (bio_is_passthrough(bio_src))
+		bio = bio_kmalloc(gfp_mask, bio_segments(bio_src));
+	else
+		bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src),
+				       &bounce_bio_set);
 	if (!bio)
 		return NULL;
 	bio->bi_disk		= bio_src->bi_disk;
@@ -294,7 +296,6 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	unsigned i = 0;
 	bool bounce = false;
 	int sectors = 0;
-	bool passthrough = bio_is_passthrough(*bio_orig);
 
 	bio_for_each_segment(from, *bio_orig, iter) {
 		if (i++ < BIO_MAX_PAGES)
@@ -305,14 +306,14 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	if (!bounce)
 		return;
 
-	if (!passthrough && sectors < bio_sectors(*bio_orig)) {
+	if (!bio_is_passthrough(*bio_orig) &&
+	    sectors < bio_sectors(*bio_orig)) {
 		bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
 		bio_chain(bio, *bio_orig);
 		submit_bio_noacct(*bio_orig);
 		*bio_orig = bio;
 	}
-	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :
-			&bounce_bio_set);
+	bio = bounce_clone_bio(*bio_orig, GFP_NOIO);
 
 	/*
 	 * Bvec table can't be updated by bio_for_each_segment_all(),
-- 
2.36.1