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block: fix bio_alloc_bioset slowpath GFP handling

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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: b520c4eef8 ("block: split bio_alloc_bioset more clearly into a fast and slowpath")
Reported-by: syzbot+09ddb593eea76a158f42@syzkaller.appspotmail.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/p01.gc6e9ad5845ad.ttca29g@ub.hpns
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Vasily Gorbik 2026-03-22 03:35:10 +01:00 committed by Jens Axboe
parent 24d4c90286
commit 67807fbaf1
1 changed files with 2 additions and 2 deletions
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4
block/bio.c
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@ -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);
}
}