On Tue, 21 Jul 2020 14:11:31 +0300 Kirill A. Shutemov wrote: > On Mon, Jul 20, 2020 at 04:51:44PM -0700, Andrew Morton wrote: > > On Sun, 19 Jul 2020 14:10:19 -0700 syzbot wrote: > > > > > syzbot has found a reproducer for the following issue on: > > > > > > HEAD commit: 4c43049f Add linux-next specific files for 20200716 > > > git tree: linux-next > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12c56087100000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2c76d72659687242 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=c48f34012b06c4ac67dd > > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1344abeb100000 > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+c48f34012b06c4ac67dd@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > Thanks. > > > > __handle_mm_fault > > ->pmd_migration_entry_wait > > ->migration_entry_to_page > > > > stumbled onto an unlocked page. > > > > I don't immediately see a cause. Perhaps Matthew's "THP prep patches", > > perhaps something else. > > > > Is it possible to perform a bisection? > > Maybe it's related to the new lock_page_async()? Or is there likely the window that after copy_huge_pmd() the src pmd migrate entry is removed and the page unlocked but the dst is not? > > > ------------[ cut here ]------------ > > > kernel BUG at include/linux/swapops.h:197! > > > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > > > CPU: 1 PID: 19938 Comm: syz-executor.2 Not tainted 5.8.0-rc5-next-20200716-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > RIP: 0010:migration_entry_to_page include/linux/swapops.h:197 [inline] > > > RIP: 0010:migration_entry_to_page include/linux/swapops.h:190 [inline] > > > RIP: 0010:pmd_migration_entry_wait+0x493/0x520 mm/migrate.c:368 > > > Code: 4d 8d 66 ff e9 1f fe ff ff e8 b9 c4 be ff 49 8d 5f ff e9 58 fe ff ff e8 ab c4 be ff 4d 8d 66 ff e9 a9 fe ff ff e8 9d c4 be ff <0f> 0b e8 96 c4 be ff 0f 0b e8 8f c4 be ff 4c 8d 65 ff eb a7 48 89 > > > RSP: 0018:ffffc9001095fb70 EFLAGS: 00010293 > > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81b56a24 > > > RDX: ffff888092022240 RSI: ffffffff81b56b43 RDI: 0000000000000001 > > > RBP: ffffea0008468080 R08: 0000000000000000 R09: ffffea0008468087 > > > R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0008468080 > > > R13: ffff888015d2e0c0 R14: 0000000000000000 R15: 0000000000000000 > > > FS: 00007f55eb477700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: 0000000020000080 CR3: 000000021ad87000 CR4: 00000000001526e0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > Call Trace: > > > __handle_mm_fault mm/memory.c:4349 [inline] > > > handle_mm_fault+0x23cf/0x45e0 mm/memory.c:4465 > > > do_user_addr_fault+0x598/0xbf0 arch/x86/mm/fault.c:1294 > > > handle_page_fault arch/x86/mm/fault.c:1351 [inline] > > > exc_page_fault+0xab/0x170 arch/x86/mm/fault.c:1404 > > > asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:544 > > > RIP: 0010:copy_user_generic_unrolled+0x89/0xc0 arch/x86/lib/copy_user_64.S:91 > > > Code: 38 4c 89 47 20 4c 89 4f 28 4c 89 57 30 4c 89 5f 38 48 8d 76 40 48 8d 7f 40 ff c9 75 b6 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a > > > RSP: 0018:ffffc9001095fe48 EFLAGS: 00010202 > > > RAX: 0000000000000001 RBX: 0000000020000080 RCX: 0000000000000001 > > > RDX: 0000000000000000 RSI: ffffc9001095fea8 RDI: 0000000020000080 > > > RBP: ffffc9001095fea8 R08: 0000000400000003 R09: ffffc9001095feaf > > > R10: fffff5200212bfd5 R11: 0000000000000000 R12: 0000000000000008 > > > R13: 0000000020000088 R14: 00007ffffffff000 R15: 0000000000000000 > > > copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline] > > > raw_copy_to_user arch/x86/include/asm/uaccess_64.h:74 [inline] > > > _copy_to_user+0x11e/0x160 lib/usercopy.c:30 > > > copy_to_user include/linux/uaccess.h:168 [inline] > > > do_pipe2+0x128/0x1b0 fs/pipe.c:1014 > > > __do_sys_pipe fs/pipe.c:1035 [inline] > > > __se_sys_pipe fs/pipe.c:1033 [inline] > > > __x64_sys_pipe+0x2f/0x40 fs/pipe.c:1033 > > > do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384 > > > entry_SYSCALL_64_after_hwframe+0x44/0xa9
