On Tue, Aug 24, 2021 at 12:14 PM Yang Shi <shy828301@xxxxxxxxx> wrote: > > On Tue, Aug 24, 2021 at 12:13 PM Yang Shi <shy828301@xxxxxxxxx> wrote: > > > > On Tue, Aug 24, 2021 at 11:17 AM syzbot > > <syzbot+f17e5ab118d29367bda9@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: d6d09a694205 Merge tag 'for-5.14-rc6-tag' of git://git.ker.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=14924605300000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=f61012d0b1cd846f > > > dashboard link: https://syzkaller.appspot.com/bug?extid=f17e5ab118d29367bda9 > > > compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1 > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+f17e5ab118d29367bda9@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > unmap_region+0x2ab/0x300 mm/mmap.c:2680 > > > __do_munmap+0x18eb/0x2050 mm/mmap.c:2911 > > > __do_sys_mremap+0x5d9/0x1390 mm/mremap.c:969 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > ------------[ cut here ]------------ > > > kernel BUG at mm/khugepaged.c:1830! > > > > The BUG means the page is not fully unmapped due to some race, just > > like what https://lore.kernel.org/linux-mm/00000000000030563005ca006ffd@xxxxxxxxxx/ > > reported. > > > > But I really don't think it is worth VM_BUG since khugepaged can just back off. In addition, I think we should be able to just replace unmap_mapping_pages() to try_to_unmap() or unmap_page (of course, make it non-static) since some races are closed by Hugh's patches. > > Forgot cc to other stakeholders. > > > > > > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > > > CPU: 0 PID: 1651 Comm: khugepaged Not tainted 5.14.0-rc6-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > RIP: 0010:collapse_file+0x3537/0x36e0 mm/khugepaged.c:1830 > > > Code: e8 1e 7a b2 ff 48 89 df 48 c7 c6 40 7b 3d 8a e8 ef 02 e8 ff 0f 0b e8 08 7a b2 ff 48 89 df 48 c7 c6 a0 7b 3d 8a e8 d9 02 e8 ff <0f> 0b e8 f2 79 b2 ff 4c 89 e7 48 c7 c6 a0 7e 3d 8a e8 c3 02 e8 ff > > > RSP: 0018:ffffc900066df820 EFLAGS: 00010046 > > > RAX: 8601299b4ae62f00 RBX: ffffea0000e4e240 RCX: ffff888018fed4c0 > > > RDX: 0000000000000000 RSI: 000000000000ffff RDI: 000000000000ffff > > > RBP: ffffc900066dfa90 R08: ffffffff81d08764 R09: ffffed1017383f2c > > > R10: ffffed1017383f2c R11: 0000000000000000 R12: ffffc900066df9d8 > > > R13: dffffc0000000000 R14: ffffc900066dfa20 R15: 0000000000000001 > > > FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: 0000000100000000 CR3: 000000000c48e000 CR4: 00000000001506f0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > Call Trace: > > > khugepaged_scan_file mm/khugepaged.c:2051 [inline] > > > khugepaged_scan_mm_slot+0x27be/0x2ad0 mm/khugepaged.c:2146 > > > khugepaged_do_scan+0x2b1/0x640 mm/khugepaged.c:2230 > > > khugepaged+0x105/0x890 mm/khugepaged.c:2275 > > > kthread+0x453/0x480 kernel/kthread.c:319 > > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 > > > Modules linked in: > > > ---[ end trace 8de2a60ea4ac5483 ]--- > > > RIP: 0010:collapse_file+0x3537/0x36e0 mm/khugepaged.c:1830 > > > Code: e8 1e 7a b2 ff 48 89 df 48 c7 c6 40 7b 3d 8a e8 ef 02 e8 ff 0f 0b e8 08 7a b2 ff 48 89 df 48 c7 c6 a0 7b 3d 8a e8 d9 02 e8 ff <0f> 0b e8 f2 79 b2 ff 4c 89 e7 48 c7 c6 a0 7e 3d 8a e8 c3 02 e8 ff > > > RSP: 0018:ffffc900066df820 EFLAGS: 00010046 > > > RAX: 8601299b4ae62f00 RBX: ffffea0000e4e240 RCX: ffff888018fed4c0 > > > RDX: 0000000000000000 RSI: 000000000000ffff RDI: 000000000000ffff > > > RBP: ffffc900066dfa90 R08: ffffffff81d08764 R09: ffffed1017383f2c > > > R10: ffffed1017383f2c R11: 0000000000000000 R12: ffffc900066df9d8 > > > R13: dffffc0000000000 R14: ffffc900066dfa20 R15: 0000000000000001 > > > FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: 0000000100000000 CR3: 000000000c48e000 CR4: 00000000001506f0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > ---------------- > > > Code disassembly (best guess): > > > 0: e8 1e 7a b2 ff callq 0xffb27a23 > > > 5: 48 89 df mov %rbx,%rdi > > > 8: 48 c7 c6 40 7b 3d 8a mov $0xffffffff8a3d7b40,%rsi > > > f: e8 ef 02 e8 ff callq 0xffe80303 > > > 14: 0f 0b ud2 > > > 16: e8 08 7a b2 ff callq 0xffb27a23 > > > 1b: 48 89 df mov %rbx,%rdi > > > 1e: 48 c7 c6 a0 7b 3d 8a mov $0xffffffff8a3d7ba0,%rsi > > > 25: e8 d9 02 e8 ff callq 0xffe80303 > > > 2a: 0f 0b ud2 <-- trapping instruction > > > 2c: e8 f2 79 b2 ff callq 0xffb27a23 > > > 31: 4c 89 e7 mov %r12,%rdi > > > 34: 48 c7 c6 a0 7e 3d 8a mov $0xffffffff8a3d7ea0,%rsi > > > 3b: e8 c3 02 e8 ff callq 0xffe80303 > > > > > > > > > --- > > > This report is generated by a bot. It may contain errors. > > > See https://goo.gl/tpsmEJ for more information about syzbot. > > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > > > syzbot will keep track of this issue. See: > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > >
