On Thu, Nov 24, 2016 at 2:49 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote: > On 11/18/2016 11:19 AM, Dmitry Vyukov wrote: >> >> 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 > > > Shouldn't there be also dump_page() output? Since you've hit this: > VM_BUG_ON_PAGE(page->pmd_huge_pte, page); Here it is: [ 250.326131] page:ffffea0000e196c0 count:1 mapcount:0 mapping: (null) index:0x0 [ 250.343393] flags: 0x1fffc0000000000() [ 250.345328] page dumped because: VM_BUG_ON_PAGE(page->pmd_huge_pte) [ 250.346780] ------------[ cut here ]------------ [ 250.347742] kernel BUG at ./include/linux/mm.h:1743! > Anyway the output wouldn't contain the value of pmd_huge_pte or stuff that's > in union with it. I'd suggest adding a local patch that prints this in the > error case, in case the fuzzer hits it again. > > Heck, it might even make sense to print raw contents of struct page in > dump_page() as a catch-all solution? Should I send a patch? Yes, please send. We are moving towards continuous build without local patches. >> 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 ]--- >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@xxxxxxxxx. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> >> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>