On 10/31/2017 01:42 PM, Dmitry Vyukov wrote: >> My vm_area_struct is 192 bytes, could be your layout is different due to >> .config. At offset 80 I have vma->vm_flags. That is checked by >> __do_page_fault(), but only after vma->vm_start (offset 0). Of course, >> reordering is possible. > > > It seems that compiler over-optimizes things and messes debug info. > I just re-reproduced this on upstream > 15f859ae5c43c7f0a064ed92d33f7a5bc5de6de0 and got the same report: > > ================================================================== > BUG: KASAN: use-after-free in arch_local_irq_enable > arch/x86/include/asm/paravirt.h:787 [inline] > BUG: KASAN: use-after-free in __do_page_fault+0xc03/0xd60 > arch/x86/mm/fault.c:1357 > Read of size 8 at addr ffff880064d19aa0 by task syz-executor/8001 > > CPU: 0 PID: 8001 Comm: syz-executor Not tainted 4.14.0-rc6+ #12 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:16 [inline] > dump_stack+0x194/0x257 lib/dump_stack.c:52 > print_address_description+0x73/0x250 mm/kasan/report.c:252 > kasan_report_error mm/kasan/report.c:351 [inline] > kasan_report+0x25b/0x340 mm/kasan/report.c:409 > __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 > arch_local_irq_enable arch/x86/include/asm/paravirt.h:787 [inline] > __do_page_fault+0xc03/0xd60 arch/x86/mm/fault.c:1357 > do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1520 > do_async_page_fault+0x82/0x110 arch/x86/kernel/kvm.c:273 > async_page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1069 > RIP: 0033:0x441bd0 > RSP: 002b:00007f2ed8229798 EFLAGS: 00010202 > RAX: 00007f2ed82297c0 RBX: 0000000000000000 RCX: 000000000000000e > RDX: 0000000000000400 RSI: 0000000020012fe0 RDI: 00007f2ed82297c0 > RBP: 0000000000748020 R08: 0000000000000400 R09: 0000000000000000 > R10: 0000000020012fee R11: 0000000000000246 R12: 00000000ffffffff > R13: 0000000000008430 R14: 00000000006ec4d0 R15: 00007f2ed822a700 > > Allocated by task 8001: > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 > save_stack+0x43/0xd0 mm/kasan/kasan.c:447 > set_track mm/kasan/kasan.c:459 [inline] > kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 > kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 > kmem_cache_alloc+0x12e/0x760 mm/slab.c:3561 > kmem_cache_zalloc include/linux/slab.h:656 [inline] > mmap_region+0x7ee/0x15a0 mm/mmap.c:1658 > do_mmap+0x69b/0xd40 mm/mmap.c:1468 > do_mmap_pgoff include/linux/mm.h:2150 [inline] > vm_mmap_pgoff+0x1de/0x280 mm/util.c:333 > SYSC_mmap_pgoff mm/mmap.c:1518 [inline] > SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1476 > SYSC_mmap arch/x86/kernel/sys_x86_64.c:99 [inline] > SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:90 > entry_SYSCALL_64_fastpath+0x1f/0xbe > > Freed by task 8007: > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 > save_stack+0x43/0xd0 mm/kasan/kasan.c:447 > set_track mm/kasan/kasan.c:459 [inline] > kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 > __cache_free mm/slab.c:3503 [inline] > kmem_cache_free+0x77/0x280 mm/slab.c:3763 > remove_vma+0x162/0x1b0 mm/mmap.c:176 > remove_vma_list mm/mmap.c:2475 [inline] > do_munmap+0x82a/0xdf0 mm/mmap.c:2714 > mmap_region+0x59e/0x15a0 mm/mmap.c:1631 > do_mmap+0x69b/0xd40 mm/mmap.c:1468 > do_mmap_pgoff include/linux/mm.h:2150 [inline] > vm_mmap_pgoff+0x1de/0x280 mm/util.c:333 > SYSC_mmap_pgoff mm/mmap.c:1518 [inline] > SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1476 > SYSC_mmap arch/x86/kernel/sys_x86_64.c:99 [inline] > SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:90 > entry_SYSCALL_64_fastpath+0x1f/0xbe > > The buggy address belongs to the object at ffff880064d19a50 > which belongs to the cache vm_area_struct of size 200 > The buggy address is located 80 bytes inside of > 200-byte region [ffff880064d19a50, ffff880064d19b18) > The buggy address belongs to the page: > page:ffffea0001934640 count:1 mapcount:0 mapping:ffff880064d19000 index:0x0 > flags: 0x100000000000100(slab) > raw: 0100000000000100 ffff880064d19000 0000000000000000 000000010000000f > raw: ffffea00018a3a60 ffffea0001940be0 ffff88006c5f79c0 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff880064d19980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff880064d19a00: fb fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb >> ffff880064d19a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff880064d19b00: fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb fb > ffff880064d19b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > > Here is disasm of the function: > https://gist.githubusercontent.com/dvyukov/5a56c66ce605168c951a321d94df6e3a/raw/538d4ce72ceb5631dfcc866ccde46c74543de1cf/gistfile1.txt > > Seems to be vma->vm_flags at offset 80. You can see it from the disasm? I can't make much of it, unfortunately, the added kasan calls obscure it a lot for me. But I suspect it might be the vma_pkey() thing which reads from vma->vm_flags. What happens when CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS is disabled? (or is it already?) Also did you try the vmacache shortcut test suggested in my previous mail? > I think the size of 200 reported by slab is OK as it can do some rounding. > Everything points to a vma object. > > >>>> The buggy address belongs to the page: >>>> page:ffffea00072ff4c0 count:1 mapcount:0 mapping:ffff8801cbfd3040 index:0x0 >>>> flags: 0x200000000000100(slab) >>>> raw: 0200000000000100 ffff8801cbfd3040 0000000000000000 000000010000000f >>>> raw: ffffea000730c7a0 ffffea00072ff7a0 ffff8801dae069c0 0000000000000000 >>>> page dumped because: kasan: bad access detected >>>> >>>> Memory state around the buggy address: >>>> ffff8801cbfd2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >>>> ffff8801cbfd3000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb >>>>> >>>>> ffff8801cbfd3080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>>> >>>> ^ >>>> ffff8801cbfd3100: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb >>>> ffff8801cbfd3180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>>> ================================================================== >>> >>> >>> I guess this is more related to mm rather than x86, so +mm maintainers. >>> This continues to happen, in particular on upstream >>> 781402340475144bb360e32bb7437fa4b84cadc3 (Oct 28). >>> >>> >>>> --- >>>> This bug is generated by a dumb bot. It may contain errors. >>>> See https://goo.gl/tpsmEJ for details. >>>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxx. >>>> >>>> syzbot will keep track of this bug report. >>>> Once a fix for this bug is committed, please 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. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google Groups >>>> "syzkaller-bugs" group. >>>> To unsubscribe from this group and stop receiving emails from it, send an >>>> email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/syzkaller-bugs/94eb2c0433c8f42cac055cc86991%40google.com. >>>> For more options, visit https://groups.google.com/d/optout. >>> >>> -- >>> 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>
