Messages in this thread | | | From | Dmitry Vyukov <> | Date | Tue, 19 Dec 2017 12:47:18 +0100 | Subject | Re: kernel BUG at mm/vmalloc.c:LINE! |
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On Tue, Dec 19, 2017 at 11:52 AM, syzbot <bot+e1e744d9e0a29be67c9a0801837ac5e6889b974a@syzkaller.appspotmail.com> 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. > > Unfortunately, I don't have any reproducer for this bug yet. > > > netlink: 2 bytes leftover after parsing attributes in process > `syz-executor6'. > ------------[ cut here ]------------ > kernel BUG at mm/vmalloc.c:1538! > invalid opcode: 0000 [#1] SMP > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 0 PID: 10625 Comm: syz-executor1 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:__vunmap+0xd6/0x150 mm/vmalloc.c:1538 > RSP: 0018:ffffc9000111fbc0 EFLAGS: 00010293 > RAX: ffff8801fd102000 RBX: ffff8801fcea6800 RCX: ffffffff813b55a6 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000286 > RBP: ffffc9000111fbe0 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801fd188600 > R13: 0000000000000000 R14: 0000000000000001 R15: ffff880215e00bd0 > FS: 0000000000f52940(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f8e70bc7410 CR3: 000000000301e006 CR4: 00000000001606f0 > DR0: 0000000020000000 DR1: 0000000020001000 DR2: 0000000020000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 > Call Trace:vfreemalloc.c:1606 > kcov_put+0x16/0x30 kernel/kcov.c:237 > kcov_close+0x10/0x20 kernel/kcov.c:322 > __fput+0x120/0x270 fs/file_table.c:209 > ____fput+0x15/0x20 fs/file_table.c:243 > task_work_run+0xa3/0xe0 kernel/task_work.c:113 > exit_task_work include/linux/task_work.h:22 [inline] > do_exit+0x3e6/0x1050 kernel/exit.c:869 > do_group_exit+0x60/0x100 kernel/exit.c:972 > get_signal+0x36c/0xad0 kernel/signal.c:2337 > do_signal+0x23/0x670 arch/x86/kernel/signal.c:809 > exit_to_usermode_loop+0x13c/0x160 arch/x86/entry/common.c:161 > prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] > syscall_return_slowpath+0x1b4/0x1e0 arch/x86/entry/common.c:264 > entry_SYSCALL_64_fastpath+0x94/0x96 > RIP: 0033:0x47e050 > RSP: 002b:0000000000a2fa08 EFLAGS: 00000246 ORIG_RAX: 0000000000000023 > RAX: fffffffffffffdfc RBX: 0000000000f52914 RCX: 000000000047e050 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000a2fa10 > RBP: 0000000000000176 R08: 0000000000000001 R09: 0000000000f52940 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 0000000000000004 R14: 0000000000010a3d R15: 0000000000000010 > Code: ef 83 c3 01 e8 cc a6 f9 ff 41 39 5c 24 28 76 41 e8 b0 4d f0 ff 49 8b > 54 24 20 48 63 c3 4c 8b 2c c2 4d 85 ed 75 d1 e8 9a 4d f0 ff <0f> 0b e8 93 4d > f0 ff 48 89 de 48 c7 c7 a0 26 e6 82 e8 84 c9 e0 > RIP: __vunmap+0xd6/0x150 mm/vmalloc.c:1538 RSP: ffffc9000111fbc0 > ---[ end trace 509bb709bc31ed41 ]---
Humm.... we've seen 3 of these in the last 4 days, all on linux-next.
The only potentially racy thing I see is vm_insert_page() after unlocking the spinlock in kcov_mmap():
spin_unlock(&kcov->lock); for (off = 0; off < size; off += PAGE_SIZE) { page = vmalloc_to_page(kcov->area + off); if (vm_insert_page(vma, vma->vm_start + off, page)) WARN_ONCE(1, "vm_insert_page() failed"); }
However, we should hold a reference to the file here, so kcov_put() should not call vfree() yet, right?
> --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@googlegroups.com. > Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com> > > syzbot will keep track of this bug report. > Once a fix for this bug is merged into any tree, reply to this email with: > #syz fix: exact-commit-title > To mark this as a duplicate of another syzbot report, please reply with: > #syz dup: exact-subject-of-another-report > If it's a one-off invalid bug report, please reply with: > #syz invalid > Note: if the crash happens again, it will cause creation of a new bug > report. > Note: all commands must start from beginning of the line in the email body.
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