bio_alloc_bioset() first strips __GFP_DIRECT_RECLAIM from the optimistic fast allocation attempt with try_alloc_gfp(). If that fast path fails, the slowpath checks saved_gfp to decide whether blocking allocation is allowed, but then still calls mempool_alloc() with the stripped gfp mask. That can lead to a NULL bio pointer being passed into bio_init(). Fix the slowpath by using saved_gfp for the bio and bvec mempool allocations. Fixes: b520c4eef83d ("block: split bio_alloc_bioset more clearly into a fast and slowpath") Reported-by: syzbot+09ddb593eea76a158f42@syzkaller.appspotmail.com Signed-off-by: Vasily Gorbik --- If this looks fine, feel free to squash it into the offending commit or pick it up separately. block/bio.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/bio.c b/block/bio.c index 5057047194c4..77067fa346d3 100644 --- a/block/bio.c +++ b/block/bio.c @@ -581,11 +581,11 @@ struct bio *bio_alloc_bioset(struct block_device *bdev, unsigned short nr_vecs, */ opf &= ~REQ_ALLOC_CACHE; - p = mempool_alloc(&bs->bio_pool, gfp); + p = mempool_alloc(&bs->bio_pool, saved_gfp); bio = p + bs->front_pad; if (nr_vecs > BIO_INLINE_VECS) { nr_vecs = BIO_MAX_VECS; - bvecs = mempool_alloc(&bs->bvec_pool, gfp); + bvecs = mempool_alloc(&bs->bvec_pool, saved_gfp); } } -- 2.53.0