Hello, syzbot found the following issue on: HEAD commit: b7213ffa0e58 qnx4: avoid stringop-overread errors git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=107afc79300000 kernel config: https://syzkaller.appspot.com/x/.config?x=6d93fe4341f98704 dashboard link: https://syzkaller.appspot.com/bug?extid=8281086e8a6fbfbd952a compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+8281086e8a6fbfbd952a@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== BUG: KASAN: use-after-free in bdev_free_inode+0x202/0x220 block/bdev.c:407 Read of size 8 at addr ffff88807b26d948 by task ksoftirqd/0/13 CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 5.15.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:256 __kasan_report mm/kasan/report.c:442 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:459 bdev_free_inode+0x202/0x220 block/bdev.c:407 i_callback+0x3f/0x70 fs/inode.c:224 rcu_do_batch kernel/rcu/tree.c:2508 [inline] rcu_core+0x7ab/0x1470 kernel/rcu/tree.c:2743 __do_softirq+0x29b/0x9c2 kernel/softirq.c:558 run_ksoftirqd kernel/softirq.c:920 [inline] run_ksoftirqd+0x2d/0x60 kernel/softirq.c:912 smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Allocated by task 9035: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] ____kasan_kmalloc mm/kasan/common.c:513 [inline] ____kasan_kmalloc mm/kasan/common.c:472 [inline] __kasan_kmalloc+0xa4/0xd0 mm/kasan/common.c:522 kmalloc_node include/linux/slab.h:609 [inline] kzalloc_node include/linux/slab.h:732 [inline] __alloc_disk_node+0x77/0x580 block/genhd.c:1238 __blk_mq_alloc_disk+0xed/0x160 block/blk-mq.c:3140 loop_add+0x340/0x960 drivers/block/loop.c:2344 loop_control_ioctl+0x130/0x4a0 drivers/block/loop.c:2512 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Freed by task 9035: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360 ____kasan_slab_free mm/kasan/common.c:366 [inline] ____kasan_slab_free mm/kasan/common.c:328 [inline] __kasan_slab_free+0xff/0x130 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:230 [inline] slab_free_hook mm/slub.c:1700 [inline] slab_free_freelist_hook+0x81/0x190 mm/slub.c:1725 slab_free mm/slub.c:3483 [inline] kfree+0xe4/0x530 mm/slub.c:4543 __alloc_disk_node+0x474/0x580 block/genhd.c:1275 __blk_mq_alloc_disk+0xed/0x160 block/blk-mq.c:3140 loop_add+0x340/0x960 drivers/block/loop.c:2344 loop_control_ioctl+0x130/0x4a0 drivers/block/loop.c:2512 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae The buggy address belongs to the object at ffff88807b26d800 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 328 bytes inside of 1024-byte region [ffff88807b26d800, ffff88807b26dc00) The buggy address belongs to the page: page:ffffea0001ec9a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b268 head:ffffea0001ec9a00 order:3 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010c41dc0 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6541, ts 204759478755, free_ts 204758542274 prep_new_page mm/page_alloc.c:2424 [inline] get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4153 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5375 alloc_pages+0x1a7/0x300 mm/mempolicy.c:2197 alloc_slab_page mm/slub.c:1763 [inline] allocate_slab mm/slub.c:1900 [inline] new_slab+0x319/0x490 mm/slub.c:1963 ___slab_alloc+0x921/0xfe0 mm/slub.c:2994 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3081 slab_alloc_node mm/slub.c:3172 [inline] __kmalloc_node_track_caller+0x2d2/0x340 mm/slub.c:4936 kmalloc_reserve net/core/skbuff.c:355 [inline] __alloc_skb+0xde/0x340 net/core/skbuff.c:426 alloc_skb include/linux/skbuff.h:1116 [inline] __tcp_send_ack.part.0+0x67/0x7a0 net/ipv4/tcp_output.c:3946 __tcp_send_ack net/ipv4/tcp_output.c:3978 [inline] tcp_send_ack+0x7d/0xa0 net/ipv4/tcp_output.c:3978 tcp_cleanup_rbuf+0x464/0x5a0 net/ipv4/tcp.c:1601 tcp_recvmsg_locked+0x7a2/0x2320 net/ipv4/tcp.c:2522 tcp_recvmsg+0x134/0x550 net/ipv4/tcp.c:2552 inet_recvmsg+0x11b/0x5e0 net/ipv4/af_inet.c:852 sock_recvmsg_nosec net/socket.c:944 [inline] sock_recvmsg net/socket.c:962 [inline] sock_recvmsg net/socket.c:958 [inline] sock_read_iter+0x353/0x490 net/socket.c:1035 call_read_iter include/linux/fs.h:2157 [inline] new_sync_read+0x590/0x6b0 fs/read_write.c:404 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1338 [inline] free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1389 free_unref_page_prepare mm/page_alloc.c:3315 [inline] free_unref_page+0x19/0x690 mm/page_alloc.c:3394 __put_page+0x105/0x400 mm/swap.c:127 put_page include/linux/mm.h:1247 [inline] __skb_frag_unref include/linux/skbuff.h:3107 [inline] skb_release_data+0x49d/0x790 net/core/skbuff.c:671 skb_release_all net/core/skbuff.c:741 [inline] __kfree_skb+0x46/0x60 net/core/skbuff.c:755 sk_eat_skb include/net/sock.h:2596 [inline] tcp_recvmsg_locked+0x12f7/0x2320 net/ipv4/tcp.c:2506 tcp_recvmsg+0x134/0x550 net/ipv4/tcp.c:2552 inet_recvmsg+0x11b/0x5e0 net/ipv4/af_inet.c:852 sock_recvmsg_nosec net/socket.c:944 [inline] sock_recvmsg net/socket.c:962 [inline] sock_recvmsg net/socket.c:958 [inline] sock_read_iter+0x353/0x490 net/socket.c:1035 call_read_iter include/linux/fs.h:2157 [inline] new_sync_read+0x590/0x6b0 fs/read_write.c:404 vfs_read+0x35c/0x600 fs/read_write.c:485 ksys_read+0x1ee/0x250 fs/read_write.c:623 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Memory state around the buggy address: ffff88807b26d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88807b26d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88807b26d900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88807b26d980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88807b26da00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb 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