On Tue, Oct 31, 2017 at 3:00 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote: > On 10/30/2017 08:15 PM, Dmitry Vyukov wrote: >> On Mon, Oct 30, 2017 at 10:12 PM, syzbot >> <bot+6a5269ce759a7bb12754ed9622076dc93f65a1f6@xxxxxxxxxxxxxxxxxxxxxxxxx> >> wrote: >>> Hello, >>> >>> syzkaller hit the following crash on >>> 887c8ba753fbe809ba93fa3cfd0cc46db18d37d4 >>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master >>> compiler: gcc (GCC) 7.1.1 20170620 >>> .config is attached >>> Raw console output is attached. >>> >>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >>> for information about syzkaller reproducers >>> >>> >>> 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 ffff8801cbfd3090 by task syz-executor7/3660 > > Why would local_irq_enable() touch a vma object? Is the stack unwinder > confused or what? > arch/x86/mm/fault.c:1357 means the "else" path of if (user_mode(regs)), > but the page fault's RIP is userspace? Strange. > >>> CPU: 1 PID: 3660 Comm: syz-executor7 Not tainted 4.14.0-rc3+ #23 >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >>> Google 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 >>> page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1066 >>> RIP: 0023:0x8073f4f >>> RSP: 002b:00000000f7f89bd0 EFLAGS: 00010202 >>> RAX: 00000000f7f89c8c RBX: 0000000000000400 RCX: 000000000000000e >>> RDX: 00000000f7f8aa88 RSI: 0000000020012fe0 RDI: 00000000f7f89c8c >>> RBP: 0000000008128000 R08: 0000000000000000 R09: 0000000000000000 >>> R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000 >>> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 >>> >>> Allocated by task 3660: >>> 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+0x6a1/0xd50 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 >>> do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline] >>> do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391 >>> entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124 >>> >>> Freed by task 3667: >>> 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+0x6a1/0xd50 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 >>> do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline] >>> do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391 >>> entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124 > > This would mean that mmap_sem is not doing its job and we raced with a > vma removal. Or the rbtree is broken and contains a vma that has been > freed. Hmm, or the vmacache is broken? You could try removing the 3 > lines starting with vmacache_find() in find_vma(). > >>> The buggy address belongs to the object at ffff8801cbfd3040 >>> which belongs to the cache vm_area_struct of size 200 >>> The buggy address is located 80 bytes inside of >>> 200-byte region [ffff8801cbfd3040, ffff8801cbfd3108) > > 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. 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>
