mm: BUG in pgtable_pmd_page_dtor

[Dmitry Vyukov]

Hello,

I've got the following BUG while running syzkaller on
a25f0944ba9b1d8a6813fd6f1a86f1bd59ac25a6 (4.9-rc5). Unfortunately it's
not reproducible.

kernel BUG at ./include/linux/mm.h:1743!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 4049 Comm: syz-fuzzer Not tainted 4.9.0-rc5+ #43
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006ad028c0 task.stack: ffff8800667e0000
RIP: 0010:[<ffffffff8130e2ab>]  [<     inline     >]
pgtable_pmd_page_dtor include/linux/mm.h:1743
RIP: 0010:[<ffffffff8130e2ab>]  [<ffffffff8130e2ab>]
___pmd_free_tlb+0x3db/0x5a0 arch/x86/mm/pgtable.c:74
RSP: 0018:ffff8800667e6908  EFLAGS: 00010292
RAX: 0000000000000000 RBX: 1ffff1000ccfcd25 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffed000ccfcd10
RBP: ffff8800667e6a70 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: 0000000000000001 R12: ffff8800667e6ef8
R13: ffff8800667e6a48 R14: ffffea0000e196c0 R15: 000000000003865b
FS:  00007f152a530700(0000) GS:ffff88006d100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1514bff9d0 CR3: 0000000009821000 CR4: 00000000000006e0
DR0: 0000000000000400 DR1: 0000000000000400 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Stack:
 0000000000000000 ffff88006ad030e0 ffff88006ad030b8 dffffc0000000000
 0000000041b58ab3 ffffffff894db568 ffffffff8130ded0 ffffffff8156b2a0
 0000000000000082 ffff88006ad030e0 1ffff1000ccfcd30 1ffff1000ccfcd38
Call Trace:
 [<     inline     >] __pmd_free_tlb arch/x86/include/asm/pgalloc.h:110
 [<     inline     >] free_pmd_range mm/memory.c:443
 [<     inline     >] free_pud_range mm/memory.c:461
 [<ffffffff81946458>] free_pgd_range+0xb98/0x1270 mm/memory.c:537
 [<ffffffff81946da5>] free_pgtables+0x275/0x340 mm/memory.c:569
 [<ffffffff81972761>] exit_mmap+0x281/0x4e0 mm/mmap.c:2942
 [<     inline     >] __mmput kernel/fork.c:866
 [<ffffffff813f24ce>] mmput+0x20e/0x4c0 kernel/fork.c:888
 [<     inline     >] exit_mm kernel/exit.c:512
 [<ffffffff814119a0>] do_exit+0x960/0x2640 kernel/exit.c:815
 [<ffffffff8141383e>] do_group_exit+0x14e/0x420 kernel/exit.c:931
 [<ffffffff814429d3>] get_signal+0x663/0x1880 kernel/signal.c:2307
 [<ffffffff81239b45>] do_signal+0xc5/0x2190 arch/x86/kernel/signal.c:807
 [<ffffffff8100666a>] exit_to_usermode_loop+0x1ea/0x2d0
arch/x86/entry/common.c:156
 [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
 [<ffffffff81009693>] syscall_return_slowpath+0x4d3/0x570
arch/x86/entry/common.c:259
 [<ffffffff881479a6>] entry_SYSCALL_64_fastpath+0xc4/0xc6
Code: 10 00 00 4c 89 e7 e8 25 6c 63 00 e9 9b fd ff ff e8 0b 9e 3d 00
0f 0b e8 04 9e 3d 00 48 c7 c6 00 ac 27 88 4c 89 f7 e8 85 9e 62 00 <0f>
0b e8 9e 2d 6e 00 e9 1a fe ff ff 48 89 cf 48 89 8d b0 fe ff
RIP  [<     inline     >] pgtable_pmd_page_dtor include/linux/mm.h:1743
RIP  [<ffffffff8130e2ab>] ___pmd_free_tlb+0x3db/0x5a0 arch/x86/mm/pgtable.c:74
 RSP <ffff8800667e6908>
---[ end trace 4ef4b70d88f62f8a ]---