On Thu, Nov 30, 2017 at 12:21 PM, Alexey Dobriyan <adobri...@gmail.com> wrote: > On 11/30/17, syzbot > <bot+d97f673cce9cfcac0a53a46127f5349b57d7a...@syzkaller.appspotmail.com> > wrote: >> Hello, >> >> syzkaller hit the following crash on >> 0c86a6bd85ff0629cd2c5141027fc1c8bb6cde9c >> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master >> compiler: gcc (GCC) 7.1.1 20170620 >> .config is attached >> Raw console output is attached. >> >> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >> for information about syzkaller reproducers >> >> >> kasan: GPF could be caused by NULL-ptr deref or user memory access >> general protection fault: 0000 [#1] SMP KASAN >> Dumping ftrace buffer: >> (ftrace buffer empty) >> Modules linked in: >> CPU: 0 PID: 3163 Comm: syz-executor1 Not tainted 4.14.0+ #190 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> task: ffff8801cbcfa440 task.stack: ffff8801cbc70000 >> RIP: 0010:proc_flush_task_mnt fs/proc/base.c:3028 [inline] >> RIP: 0010:proc_flush_task+0x26d/0x6c0 fs/proc/base.c:3100 >> RSP: 0018:ffff8801cbc77408 EFLAGS: 00010246 >> RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffed003978ee95 >> RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 1ffff1003978ee53 >> RBP: ffff8801cbc77510 R08: 0000000000000000 R09: 1ffff1003978ee0c >> R10: 0000000000000500 R11: 0000000000000000 R12: ffff8801cbc774a8 >> R13: 0000000000000000 R14: ffff8801c87fce80 R15: ffff8801cbc77468 >> FS: 00000000012dc940(0000) GS:ffff8801db400000(0000) >> knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00000000208e5ff0 CR3: 00000001cbed4000 CR4: 00000000001406f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> release_task+0x258/0x1a40 kernel/exit.c:195 >> wait_task_zombie kernel/exit.c:1161 [inline] >> wait_consider_task+0x2a10/0x3420 kernel/exit.c:1388 >> do_wait_thread kernel/exit.c:1451 [inline] >> do_wait+0x427/0xa70 kernel/exit.c:1522 >> kernel_wait4+0x1f5/0x370 kernel/exit.c:1665 >> SYSC_wait4+0x134/0x140 kernel/exit.c:1677 >> SyS_wait4+0x2c/0x40 kernel/exit.c:1673 >> entry_SYSCALL_64_fastpath+0x1f/0x96 >> RIP: 0033:0x40cbfa >> RSP: 002b:0000000000a6fa28 EFLAGS: 00000246 ORIG_RAX: 000000000000003d >> RAX: ffffffffffffffda RBX: 00000000012dc914 RCX: 000000000040cbfa >> RDX: 0000000040000001 RSI: 0000000000a6fa4c RDI: ffffffffffffffff >> RBP: 0000000000000086 R08: 0000000000000001 R09: 00000000012dc940 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 >> R13: 000000000000000a R14: 00000000001a0347 R15: 0000000000000016 >> Code: 7d a0 e8 17 2c 43 03 48 8b 8d 10 ff ff ff 0f b6 11 38 95 33 ff ff ff >> >> 7c 08 84 d2 0f 85 73 03 00 00 89 45 9c 4c 89 e8 48 c1 e8 03 <80> 3c 18 00 >> 0f 85 52 03 00 00 49 8b 7d 00 4c 89 e6 e8 8d 93 e7 >> RIP: proc_flush_task_mnt fs/proc/base.c:3028 [inline] RSP: ffff8801cbc77408 >> RIP: proc_flush_task+0x26d/0x6c0 fs/proc/base.c:3100 RSP: ffff8801cbc77408 > > same here? > > cmp BYTE PTR [rax+rbx*1],0x0 > > RAX 0 > RBX dffffc0000000000
Tat's how dereference on a NULL pointer looks with KASAN. Kernel code tries to dereference a NULL pointer.