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Subject[PATCH 5.3 027/105] block: check bi_size overflow before merge
Date
From: Junichi Nomura <j-nomura@ce.jp.nec.com>

[ Upstream commit e3a5d8e386c3fb973fa75f2403622a8f3640ec06 ]

__bio_try_merge_page() may merge a page to bio without bio_full() check
and cause bi_size overflow.

The overflow typically ends up with sd_init_command() warning on zero
segment request with call trace like this:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 1986 at drivers/scsi/scsi_lib.c:1025 scsi_init_io+0x156/0x180
CPU: 2 PID: 1986 Comm: kworker/2:1H Kdump: loaded Not tainted 5.4.0-rc7 #1
Workqueue: kblockd blk_mq_run_work_fn
RIP: 0010:scsi_init_io+0x156/0x180
RSP: 0018:ffffa11487663bf0 EFLAGS: 00010246
RAX: 00000000002be0a0 RBX: ffff8e6e9ff30118 RCX: 0000000000000000
RDX: 00000000ffffffe1 RSI: 0000000000000000 RDI: ffff8e6e9ff30118
RBP: ffffa11487663c18 R08: ffffa11487663d28 R09: ffff8e6e9ff30150
R10: 0000000000000001 R11: 0000000000000000 R12: ffff8e6e9ff30000
R13: 0000000000000001 R14: ffff8e74a1cf1800 R15: ffff8e6e9ff30000
FS: 0000000000000000(0000) GS:ffff8e6ea7680000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff18cf0fe8 CR3: 0000000659f0a001 CR4: 00000000001606e0
Call Trace:
sd_init_command+0x326/0xb40 [sd_mod]
scsi_queue_rq+0x502/0xaa0
? blk_mq_get_driver_tag+0xe7/0x120
blk_mq_dispatch_rq_list+0x256/0x5a0
? elv_rb_del+0x24/0x30
? deadline_remove_request+0x7b/0xc0
blk_mq_do_dispatch_sched+0xa3/0x140
blk_mq_sched_dispatch_requests+0xfb/0x170
__blk_mq_run_hw_queue+0x81/0x130
blk_mq_run_work_fn+0x1b/0x20
process_one_work+0x179/0x390
worker_thread+0x4f/0x3e0
kthread+0x105/0x140
? max_active_store+0x80/0x80
? kthread_bind+0x20/0x20
ret_from_fork+0x35/0x40
---[ end trace f9036abf5af4a4d3 ]---
blk_update_request: I/O error, dev sdd, sector 2875552 op 0x1:(WRITE) flags 0x0 phys_seg 0 prio class 0
XFS (sdd1): writeback error on sector 2875552

__bio_try_merge_page() should check the overflow before actually doing
merge.

Fixes: 07173c3ec276c ("block: enable multipage bvecs")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index 299a0e7651ec0..31d56e7e2ce05 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -769,7 +769,7 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
return false;

- if (bio->bi_vcnt > 0) {
+ if (bio->bi_vcnt > 0 && !bio_full(bio, len)) {
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];

if (page_is_mergeable(bv, page, len, off, same_page)) {
--
2.20.1


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