On 09/06/2016 11:03 PM, Kees Cook wrote:
On Sat, Sep 3, 2016 at 8:15 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:Hello, While running syzkaller fuzzer I've got the following GPF: general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 2 PID: 4268 Comm: syz-executor Not tainted 4.8.0-rc3-next-20160825+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88006a6527c0 task.stack: ffff880052630000 RIP: 0010:[<ffffffff82e1ccd6>] [<ffffffff82e1ccd6>] __list_add_valid+0x26/0xd0 lib/list_debug.c:23 RSP: 0018:ffff880052637a18 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90001c87000 RDX: 0000000000000001 RSI: ffff88001344cdb0 RDI: 0000000000000008 RBP: ffff880052637a30 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffffffff8a5deee0 R12: ffff88006cc47230 R13: ffff88001344cdb0 R14: ffff88006cc47230 R15: 0000000000000000 FS: 00007fbacc97e700(0000) GS:ffff88006d200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020de7000 CR3: 000000003c4d2000 CR4: 00000000000006e0 DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Stack: ffff88006cc47200 ffff88001344cd98 ffff88006cc47200 ffff880052637a78 ffffffff817bc6d1 ffff88006cc47208 ffffed000d988e41 ffff88006cc47208 ffff88006cc3e680 ffffc900035b7000 ffffc900035a7000 ffff88006cc47200 Call Trace: [< inline >] __list_add_rcu include/linux/rculist.h:51 [< inline >] list_add_rcu include/linux/rculist.h:78 [<ffffffff817bc6d1>] __insert_vmap_area+0x1c1/0x3c0 mm/vmalloc.c:340 [<ffffffff817bf544>] alloc_vmap_area+0x614/0x890 mm/vmalloc.c:458 [<ffffffff817bf8a8>] __get_vm_area_node+0xe8/0x340 mm/vmalloc.c:1377 [<ffffffff817c332a>] __vmalloc_node_range+0xaa/0x6d0 mm/vmalloc.c:1687 [< inline >] __vmalloc_node mm/vmalloc.c:1736 [<ffffffff817c39ab>] __vmalloc+0x5b/0x70 mm/vmalloc.c:1742 [<ffffffff8166ae9c>] bpf_prog_alloc+0x3c/0x190 kernel/bpf/core.c:82 [<ffffffff85c40ba9>] bpf_prog_create_from_user+0xa9/0x2c0 net/core/filter.c:1132 [< inline >] seccomp_prepare_filter kernel/seccomp.c:373 [< inline >] seccomp_prepare_user_filter kernel/seccomp.c:408 [< inline >] seccomp_set_mode_filter kernel/seccomp.c:737 [<ffffffff815d7687>] do_seccomp+0x317/0x1800 kernel/seccomp.c:787 [<ffffffff815d8f84>] prctl_set_seccomp+0x34/0x60 kernel/seccomp.c:830 [< inline >] SYSC_prctl kernel/sys.c:2157 [<ffffffff813ccf8f>] SyS_prctl+0x82f/0xc80 kernel/sys.c:2075 [<ffffffff86e10700>] entry_SYSCALL_64_fastpath+0x23/0xc1 Code: 00 00 00 00 00 55 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 54 49 89 fc 48 8d 7a 08 53 48 89 d3 48 89 fa 48 83 ec 08 48 c1 ea 03 <80> 3c 02 00 75 7c 48 8b 53 08 48 39 f2 75 37 48 89 f2 48 b8 00 RIP [<ffffffff82e1ccd6>] __list_add_valid+0x26/0xd0 lib/list_debug.c:23 RSP <ffff880052637a18> ---[ end trace 983e625f02f00d9f ]--- Kernel panic - not syncing: Fatal exception On commit 0f98f121e1670eaa2a2fbb675e07d6ba7f0e146f of linux-next. Unfortunately it is not reproducible.
Can you elaborate? You hit this only once and then never again in this or some other, similar call-trace form, right?
The crashing line is: CHECK_DATA_CORRUPTION(next->prev != prev, It crashed on KASAN check at (%rax, %rdx), this address corresponds to next address = 0x8. So next was ~NULL.Paul, the RCU torture tests passed with the CONFIG_DEBUG_LIST changes, IIRC, yes? I'd love to rule out some kind of race condition between the removal and add code for the checking. Daniel, IIRC there was some talk about RCU and BPF? Am I remembering
--verbose, what talk specifically? There were some fixes longer time ago, but related to eBPF, not cBPF, but even there I don't see currently how it could be related to a va->list corruption triggered in __insert_vmap_area().
that correctly? I'm having a hard time imagining how a list add could fail (maybe a race between two adds)?
Or some use after free that would have corrupted that memory? I would think right now that the path via bpf_prog_alloc() could have triggered, but not necessarily caused the issue, hmm. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>