Hello, syzbot found the following crash on: HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=120b26c1100000 kernel config: https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312 dashboard link: https://syzkaller.appspot.com/bug?extid=7d2debdcdb3cb93c1e5e compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1724b246100000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ceb3de100000 The bug was bisected to: commit 76313c70c52f930af4afd21684509ca52297ea71 Author: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Date: Wed Feb 19 16:37:15 2020 +0000 uml: Create a private mount of proc for mconsole bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=117c4912100000 final crash: https://syzkaller.appspot.com/x/report.txt?x=137c4912100000 console output: https://syzkaller.appspot.com/x/log.txt?x=157c4912100000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+7d2debdcdb3cb93c1e5e@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 76313c70c52f ("uml: Create a private mount of proc for mconsole") ================================================================== BUG: KASAN: use-after-free in atomic64_inc include/asm-generic/atomic-instrumented.h:1049 [inline] BUG: KASAN: use-after-free in atomic_long_inc include/asm-generic/atomic-long.h:160 [inline] BUG: KASAN: use-after-free in fsnotify_detach_connector_from_object+0x25e/0x380 fs/notify/mark.c:185 Write of size 8 at addr ffff88809fd7e7c0 by task syz-executor972/8021 CPU: 1 PID: 8021 Comm: syz-executor972 Not tainted 5.7.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 check_memory_region_inline mm/kasan/generic.c:186 [inline] check_memory_region+0x141/0x190 mm/kasan/generic.c:192 atomic64_inc include/asm-generic/atomic-instrumented.h:1049 [inline] atomic_long_inc include/asm-generic/atomic-long.h:160 [inline] fsnotify_detach_connector_from_object+0x25e/0x380 fs/notify/mark.c:185 fsnotify_put_mark+0x367/0x580 fs/notify/mark.c:250 fsnotify_clear_marks_by_group+0x33f/0x490 fs/notify/mark.c:764 fsnotify_destroy_group+0xc9/0x300 fs/notify/group.c:61 inotify_release+0x33/0x40 fs/notify/inotify/inotify_user.c:271 __fput+0x33e/0x880 fs/file_table.c:281 task_work_run+0xf4/0x1b0 kernel/task_work.c:123 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0xb3f/0x2de0 kernel/exit.c:806 do_group_exit+0x125/0x340 kernel/exit.c:904 __do_sys_exit_group kernel/exit.c:915 [inline] __se_sys_exit_group kernel/exit.c:913 [inline] __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:913 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x445448 Code: Bad RIP value. RSP: 002b:00007ffe48521018 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445448 RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 RBP: 00000000004cca90 R08: 00000000000000e7 R09: ffffffffffffffd0 R10: 00007ffe48521060 R11: 0000000000000246 R12: 0000000000000001 R13: 00000000006e0340 R14: 0000000000000007 R15: 000000000000002d Allocated by task 8026: save_stack+0x1b/0x40 mm/kasan/common.c:48 set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc mm/kasan/common.c:494 [inline] __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:669 [inline] alloc_super+0x52/0x9d0 fs/super.c:203 sget_fc+0x13f/0x790 fs/super.c:530 vfs_get_super+0x6d/0x2d0 fs/super.c:1186 vfs_get_tree+0x89/0x2f0 fs/super.c:1547 do_new_mount fs/namespace.c:2874 [inline] do_mount+0x1306/0x1b40 fs/namespace.c:3199 __do_sys_mount fs/namespace.c:3409 [inline] __se_sys_mount fs/namespace.c:3386 [inline] __x64_sys_mount+0x18f/0x230 fs/namespace.c:3386 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 Freed by task 23: save_stack+0x1b/0x40 mm/kasan/common.c:48 set_track mm/kasan/common.c:56 [inline] kasan_set_free_info mm/kasan/common.c:316 [inline] __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455 __cache_free mm/slab.c:3426 [inline] kfree+0x109/0x2b0 mm/slab.c:3757 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268 worker_thread+0x96/0xe20 kernel/workqueue.c:2414 kthread+0x388/0x470 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351 The buggy address belongs to the object at ffff88809fd7e000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 1984 bytes inside of 4096-byte region [ffff88809fd7e000, ffff88809fd7f000) The buggy address belongs to the page: page:ffffea00027f5f80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea00027f5f80 order:1 compound_mapcount:0 flags: 0xfffe0000010200(slab|head) raw: 00fffe0000010200 ffffea000247aa88 ffffea000242ef08 ffff8880aa002000 raw: 0000000000000000 ffff88809fd7e000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809fd7e680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809fd7e700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88809fd7e780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88809fd7e800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88809fd7e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
