[+Cc aarcange@xxxxxxxxxx, linux-mm@xxxxxxxxx] On Fri, Dec 22, 2017 at 01:37:01PM -0800, syzbot wrote: > Hello, > > syzkaller hit the following crash on > 6084b576dca2e898f5c101baef151f7bfdbb606d > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. > C reproducer is attached > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > for information about syzkaller reproducers > > > ------------[ cut here ]------------ > kernel BUG at fs/userfaultfd.c:142! > invalid opcode: 0000 [#1] SMP > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 0 PID: 3118 Comm: syzkaller879466 Not tainted 4.15.0-rc3-next-20171214+ > #67 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:userfaultfd_ctx_get+0x6d/0x70 fs/userfaultfd.c:142 > RSP: 0000:ffffc900012f7c30 EFLAGS: 00010293 > RAX: ffff8802134420c0 RBX: 0000000000000000 RCX: ffffffff8147a98d > RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffff880213659c40 > RBP: ffffc900012f7c48 R08: 0000000000000000 R09: 0000000000000004 > R10: ffffc900012f7cc0 R11: 0000000000000004 R12: ffff880213659c40 > R13: ffff880214ed6000 R14: 0000000000000200 R15: 0000000000000000 > FS: 00007fdf76164700(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020687000 CR3: 0000000211d48006 CR4: 00000000001606f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > handle_userfault+0xd3/0xa00 fs/userfaultfd.c:445 > do_huge_pmd_anonymous_page+0x571/0x850 mm/huge_memory.c:707 > create_huge_pmd mm/memory.c:3838 [inline] > __handle_mm_fault+0xc37/0x1930 mm/memory.c:4042 > handle_mm_fault+0x215/0x450 mm/memory.c:4108 > __do_page_fault+0x337/0x6b0 arch/x86/mm/fault.c:1429 > do_page_fault+0x52/0x330 arch/x86/mm/fault.c:1504 > page_fault+0x4c/0x60 arch/x86/entry/entry_64.S:1243 > RIP: 0033:0x4453e5 > RSP: 002b:0000000020687000 EFLAGS: 00010217 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000004453d9 > RDX: 0000000020b4c000 RSI: 0000000020687000 RDI: 0000000000000600 > RBP: 0000000000000000 R08: 00000000207a4f71 R09: 00007fdf76164700 > R10: 0000000020552ffc R11: 0000000000000202 R12: 0000000000000000 > R13: 00007ffc6b2b2c2f R14: 00007fdf761649c0 R15: 0000000000000000 > Code: 5b 41 5c 41 5d 5d c3 e8 d2 f9 e3 ff 85 db 74 16 e8 c9 f9 e3 ff 8d 53 > 01 89 d8 f0 41 0f b1 55 00 89 c3 74 d7 eb e1 e8 b3 f9 e3 ff <0f> 0b 90 55 48 > 89 e5 53 48 89 fb e8 a3 f9 e3 ff 48 83 3d 73 bb > RIP: userfaultfd_ctx_get+0x6d/0x70 fs/userfaultfd.c:142 RSP: > ffffc900012f7c30 > ---[ end trace c25da3c687899c5a ]--- > Kernel panic - not syncing: Fatal exception > Dumping ftrace buffer: > (ftrace buffer empty) > Kernel Offset: disabled > Rebooting in 86400 seconds.. > > Possibly a duplicate of "KASAN: use-after-free Read in handle_userfault": https://groups.google.com/d/msg/syzkaller-bugs/sS99S-Z-9No/O4dwVMtVAQAJ (which *really* needs to be fixed, by the way. Who is maintaining the "userfaultfd" feature?) Eric
