On Wed, Sep 7, 2016 at 1:11 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > 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? Correct. >>> 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. That's highly likely. -- 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>