On 20/03/2019 09:12, Hannes Reinecke wrote:
> __blkdev_direct_IO_simple() is allocating a bio on the stack.
> When that bio needs to be split bio_chain_endio() invokes bio_put()
> on this bio, causing the kernel to crash in mempool_free() as the
> bio was never allocated from a mempool in the first place.
> So call bio_get() before submitting to avoid this problem.
Hmm this sounds as if we're just papering over the real issue here,
which is calling bio_free() for bios not allocated using bio_alloc_bioset().
How about the following untested patch:
>From 9c8434e5bf81595e97ea5647437d12bfce0e37b6 Mon Sep 17 00:00:00 2001
From: Johannes Thumshirn <jthumshirn@xxxxxxx>
Date: Wed, 20 Mar 2019 09:40:18 +0100
Subject: [PATCH] bio: Introduce BIO_ALLOCED flag and check it in bio_free
When we're submitting a bio from stack and this ends up being split, we
call bio_put(). bio_put() will eventually call bio_free() if the reference
count drops to 0. But freeing the bio is wrong, as it was never allocated
out of the bio's mempool.
Flag each normally allocated bio as 'BIO_ALLOCATED' and skip freeing if the
flag isn't set.
Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
---
block/bio.c | 4 ++++
include/linux/blk_types.h | 1 +
2 files changed, 5 insertions(+)
diff --git a/block/bio.c b/block/bio.c
index 4db1008309ed..caa8bc076377 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -253,6 +253,9 @@ static void bio_free(struct bio *bio)
struct bio_set *bs = bio->bi_pool;
void *p;
+ if (!bio_flagged(bio, BIO_ALLOCED))
+ return;
+
bio_uninit(bio);
if (bs) {
@@ -521,6 +524,7 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask,
unsigned int nr_iovecs,
bvl = bio->bi_inline_vecs;
}
+ bio_set_flag(bio, BIO_ALLOCED);
bio->bi_pool = bs;
bio->bi_max_vecs = nr_iovecs;
bio->bi_io_vec = bvl;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d66bf5f32610..14b4f87a1eab 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -229,6 +229,7 @@ struct bio {
* of this bio. */
#define BIO_QUEUE_ENTERED 11 /* can use blk_queue_enter_live() */
#define BIO_TRACKED 12 /* set if bio goes through the rq_qos path */
+#define BIO_ALLOCED 13 /* set if the bio was allocated by
bio_alloc_bioset */
/* See BVEC_POOL_OFFSET below before adding new flags */
--
2.16.4
--
Johannes Thumshirn SUSE Labs Filesystems
jthumshirn@xxxxxxx +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
