Hello, syzbot found the following issue on: HEAD commit: 009fc857 mISDN: fix possible use-after-free in HFC_cleanup() git tree: net-next console output: https://syzkaller.appspot.com/x/log.txt?x=11ce90add00000 kernel config: https://syzkaller.appspot.com/x/.config?x=b072be26137971e1 dashboard link: https://syzkaller.appspot.com/bug?extid=0f7e7e5e2f4f40fa89c0 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17c9f9b3d00000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0f7e7e5e2f4f40fa89c0@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== BUG: KASAN: use-after-free in bcm_rx_starttimer net/can/bcm.c:543 [inline] BUG: KASAN: use-after-free in bcm_rx_handler+0x5ff/0x6d0 net/can/bcm.c:694 Read of size 4 at addr ffff88802af28418 by task syz-executor.1/10095 CPU: 1 PID: 10095 Comm: syz-executor.1 Not tainted 5.12.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x141/0x1d7 lib/dump_stack.c:120 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233 __kasan_report mm/kasan/report.c:419 [inline] kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436 bcm_rx_starttimer net/can/bcm.c:543 [inline] bcm_rx_handler+0x5ff/0x6d0 net/can/bcm.c:694 deliver net/can/af_can.c:574 [inline] can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635 can_receive+0x290/0x580 net/can/af_can.c:661 can_rcv+0x120/0x1c0 net/can/af_can.c:696 __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5440 __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5554 process_backlog+0x232/0x6c0 net/core/dev.c:6418 __napi_poll+0xaf/0x440 net/core/dev.c:6966 napi_poll net/core/dev.c:7033 [inline] net_rx_action+0x801/0xb40 net/core/dev.c:7120 __do_softirq+0x29b/0x9f6 kernel/softirq.c:559 do_softirq.part.0+0xd9/0x130 kernel/softirq.c:460 </IRQ> netif_rx_ni+0x33d/0x590 net/core/dev.c:4966 can_send+0x4ec/0x9a0 net/can/af_can.c:287 isotp_sendmsg+0x8c2/0x13d0 net/can/isotp.c:946 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4665f9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff4a7a7d188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665f9 RDX: 0000000000000004 RSI: 00000000200003c0 RDI: 0000000000000004 RBP: 00000000004bfce1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffe23e0924f R14: 00007ff4a7a7d300 R15: 0000000000022000 Allocated by task 10111: 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:428 [inline] ____kasan_kmalloc mm/kasan/common.c:507 [inline] ____kasan_kmalloc mm/kasan/common.c:466 [inline] __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:516 kmalloc include/linux/slab.h:556 [inline] kzalloc include/linux/slab.h:686 [inline] bcm_rx_setup net/can/bcm.c:1070 [inline] bcm_sendmsg+0x2a81/0x4420 net/can/bcm.c:1331 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae Freed by task 10093: 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:357 ____kasan_slab_free mm/kasan/common.c:360 [inline] ____kasan_slab_free mm/kasan/common.c:325 [inline] __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:368 kasan_slab_free include/linux/kasan.h:212 [inline] slab_free_hook mm/slub.c:1581 [inline] slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1606 slab_free mm/slub.c:3166 [inline] kfree+0xe5/0x7f0 mm/slub.c:4225 bcm_release+0x34a/0x780 net/can/bcm.c:1506 __sock_release+0xcd/0x280 net/socket.c:599 sock_close+0x18/0x20 net/socket.c:1258 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x272/0x280 kernel/entry/common.c:208 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:57 entry_SYSCALL_64_after_hwframe+0x44/0xae The buggy address belongs to the object at ffff88802af28400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 24 bytes inside of 512-byte region [ffff88802af28400, ffff88802af28600) The buggy address belongs to the page: page:ffffea0000abca00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2af28 head:ffffea0000abca00 order:2 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888011041c80 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 8455, ts 309324953429, free_ts 309319650475 prep_new_page mm/page_alloc.c:2358 [inline] get_page_from_freelist+0x1033/0x2b60 mm/page_alloc.c:3994 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5200 alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272 alloc_slab_page mm/slub.c:1644 [inline] allocate_slab+0x2c5/0x4c0 mm/slub.c:1784 new_slab mm/slub.c:1847 [inline] new_slab_objects mm/slub.c:2593 [inline] ___slab_alloc+0x44c/0x7a0 mm/slub.c:2756 __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2796 slab_alloc_node mm/slub.c:2878 [inline] __kmalloc_node_track_caller+0x2e6/0x350 mm/slub.c:4604 kmalloc_reserve net/core/skbuff.c:354 [inline] __alloc_skb+0xde/0x340 net/core/skbuff.c:425 alloc_skb include/linux/skbuff.h:1107 [inline] nlmsg_new include/net/netlink.h:953 [inline] netlink_ack+0x1ed/0xaa0 net/netlink/af_netlink.c:2437 netlink_rcv_skb+0x33d/0x420 net/netlink/af_netlink.c:2508 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:674 __sys_sendto+0x21c/0x320 net/socket.c:1977 __do_sys_sendto net/socket.c:1989 [inline] __se_sys_sendto net/socket.c:1985 [inline] __x64_sys_sendto+0xdd/0x1b0 net/socket.c:1985 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 page last free stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1298 [inline] __free_pages_ok+0x476/0xce0 mm/page_alloc.c:1572 stack_depot_save+0x162/0x4e0 lib/stackdepot.c:336 kasan_save_stack+0x32/0x40 mm/kasan/common.c:40 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:428 [inline] __kasan_slab_alloc+0x84/0xa0 mm/kasan/common.c:461 kasan_slab_alloc include/linux/kasan.h:236 [inline] slab_post_alloc_hook mm/slab.h:524 [inline] slab_alloc_node mm/slub.c:2912 [inline] slab_alloc mm/slub.c:2920 [inline] kmem_cache_alloc+0x152/0x3a0 mm/slub.c:2925 alloc_inode+0x161/0x230 fs/inode.c:235 new_inode_pseudo fs/inode.c:934 [inline] new_inode+0x27/0x2f0 fs/inode.c:963 debugfs_get_inode+0x1a/0x130 fs/debugfs/inode.c:69 __debugfs_create_file+0x11a/0x4e0 fs/debugfs/inode.c:404 debugfs_create_mode_unsafe fs/debugfs/file.c:407 [inline] debugfs_create_bool+0x6c/0xa0 fs/debugfs/file.c:862 nsim_dev_debugfs_init drivers/net/netdevsim/dev.c:231 [inline] nsim_dev_probe+0xa9d/0x1080 drivers/net/netdevsim/dev.c:1109 really_probe+0x291/0xf60 drivers/base/dd.c:576 driver_probe_device+0x298/0x410 drivers/base/dd.c:763 __device_attach_driver+0x203/0x2c0 drivers/base/dd.c:870 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 __device_attach+0x228/0x4b0 drivers/base/dd.c:938 Memory state around the buggy address: ffff88802af28300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88802af28380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88802af28400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88802af28480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802af28500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb 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