linux-kernel - Re: [syzbot] [block?] general protection fault in bio_first

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Date: Sat, 16 Dec 2023 15:00:12 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+8b23309d5788a79d3eea@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] general protection fault in bio_first_folio

On Fri, 15 Dec 2023 21:20:22 -0800
> HEAD commit:    abb240f7a2bd Add linux-next specific files for 20231212
> git tree:       linux-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13274512e80000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  abb240f7a2bd

--- x/block/blk-map.c
+++ y/block/blk-map.c
@@ -269,6 +269,7 @@ static int bio_map_user_iov(struct reque
 	unsigned int max_sectors = queue_max_hw_sectors(rq->q);
 	unsigned int nr_vecs = iov_iter_npages(iter, BIO_MAX_VECS);
 	struct bio *bio;
+	int add_pg = 0;
 	int ret;
 	int j;
 
@@ -322,6 +323,7 @@ static int bio_map_user_iov(struct reque
 					bio_release_page(bio, page);
 				bytes -= n;
 				offs = 0;
+				add_pg = 1;
 			}
 		}
 		/*
@@ -344,7 +346,8 @@ static int bio_map_user_iov(struct reque
 	return 0;
 
  out_unmap:
-	bio_release_pages(bio, false);
+	if (add_pg)
+		bio_release_pages(bio, false);
 	blk_mq_map_bio_put(bio);
 	return ret;
 }
--