Re: [PATCHv3 1/2] mm: introduce vm_ops->map_pages()

From: Sasha Levin
Date: Thu Jul 24 2014 - 09:06:13 EST

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On 07/23/2014 11:33 PM, Sasha Levin wrote:
> On 02/27/2014 02:53 PM, Kirill A. Shutemov wrote:
>> > The patch introduces new vm_ops callback ->map_pages() and uses it for
>> > mapping easy accessible pages around fault address.
>> >
>> > On read page fault, if filesystem provides ->map_pages(), we try to map
>> > up to FAULT_AROUND_PAGES pages around page fault address in hope to
>> > reduce number of minor page faults.
>> >
>> > We call ->map_pages first and use ->fault() as fallback if page by the
>> > offset is not ready to be mapped (cold page cache or something).
>> >
>> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>> > ---
> Hi all,
>
> This patch triggers use-after-free when fuzzing using trinity and the KASAN
> patchset.

FWIW, if it helps, here's another KASAN report with the conventional BUG following it:

[ 360.498001] ==================================================================
[ 360.500896] AddressSanitizer: use after free in do_read_fault.isra.40+0x3c2/0x510 at addr ffff880581ee3fd0
[ 360.504474] page:ffffea001607b8c0 count:0 mapcount:0 mapping: (null) index:0x0
[ 360.507264] page flags: 0xefffff80000000()
[ 360.508655] page dumped because: kasan error
[ 360.509489] CPU: 8 PID: 9251 Comm: trinity-c159 Not tainted 3.16.0-rc6-next-20140723-sasha-00047-g289342b-dirty #929
[ 360.511717] 00000000000000ff 0000000000000000 ffffea001607b8c0 ffff8801ba8bbb98
[ 360.513272] ffffffff8fe40903 ffff8801ba8bbc68 ffff8801ba8bbc58 ffffffff8b42acfc
[ 360.514729] 0000000000000001 ffff880592deaa48 ffff8801ba84b038 ffff8801ba8bbbd0
[ 360.516156] Call Trace:
[ 360.516622] dump_stack (lib/dump_stack.c:52)
[ 360.517566] kasan_report_error (mm/kasan/report.c:98 mm/kasan/report.c:166)
[ 360.518745] ? debug_smp_processor_id (lib/smp_processor_id.c:57)
[ 360.519923] ? preempt_count_sub (kernel/sched/core.c:2606)
[ 360.521124] ? put_lock_stats.isra.13 (./arch/x86/include/asm/preempt.h:98 kernel/locking/lockdep.c:254)
[ 360.522431] ? do_read_fault.isra.40 (mm/memory.c:2784 mm/memory.c:2849 mm/memory.c:2898)
[ 360.523651] __asan_load8 (mm/kasan/kasan.c:364)
[ 360.524625] ? do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
[ 360.525887] do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
[ 360.527156] ? __rcu_read_unlock (kernel/rcu/update.c:101)
[ 360.528251] handle_mm_fault (mm/memory.c:3092 mm/memory.c:3225 mm/memory.c:3345 mm/memory.c:3374)
[ 360.529308] ? vmacache_update (mm/vmacache.c:61)
[ 360.530505] ? find_vma (mm/mmap.c:2027)
[ 360.531453] __do_page_fault (arch/x86/mm/fault.c:1231)
[ 360.532503] ? context_tracking_user_exit (kernel/context_tracking.c:184)
[ 360.533744] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
[ 360.535001] ? trace_hardirqs_off_caller (kernel/locking/lockdep.c:2639 (discriminator 8))
[ 360.536262] ? trace_hardirqs_off (kernel/locking/lockdep.c:2645)
[ 360.537360] trace_do_page_fault (arch/x86/mm/fault.c:1314 include/linux/jump_label.h:115 include/linux/context_tracking_state.h:27 include/linux/context_tracking.h:45 arch/x86/mm/fault.c:1315)
[ 360.538493] do_async_page_fault (arch/x86/kernel/kvm.c:279)
[ 360.539567] async_page_fault (arch/x86/kernel/entry_64.S:1321)
[ 360.540668] Read of size 8 by thread T9251:
[ 360.541485] Memory state around the buggy address:
[ 360.542463] ffff880581ee3d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.543816] ffff880581ee3d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.545116] ffff880581ee3e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.546476] ffff880581ee3e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.547806] ffff880581ee3f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.549112] >ffff880581ee3f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 360.550507] ^
[ 360.551574] ffff880581ee4000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 360.552910] ffff880581ee4080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 360.554207] ffff880581ee4100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 360.555621] ffff880581ee4180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 360.557035] ffff880581ee4200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 360.558489] ==================================================================
[ 360.559804] BUG: unable to handle kernel paging request at ffff880581ee3fd0
[ 360.559817] IP: do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
[ 360.559827] PGD 147b9067 PUD 70353d067 PMD 70352d067 PTE 8000000581ee3060
[ 360.559836] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[ 360.559892] Dumping ftrace buffer:
[ 360.560117] (ftrace buffer empty)
[ 360.560132] Modules linked in:
[ 360.560145] CPU: 8 PID: 9251 Comm: trinity-c159 Not tainted 3.16.0-rc6-next-20140723-sasha-00047-g289342b-dirty #929
[ 360.560154] task: ffff8801ba84b000 ti: ffff8801ba8b8000 task.ti: ffff8801ba8b8000
[ 360.560172] RIP: do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
[ 360.560180] RSP: 0000:ffff8801ba8bbc98 EFLAGS: 00010296
[ 360.560186] RAX: 0000000000000000 RBX: ffff8801ba8d5a00 RCX: 0000000000000006
[ 360.560192] RDX: 0000000000000006 RSI: ffffffff912f5fd5 RDI: 0000000000000282
[ 360.560199] RBP: ffff8801ba8bbd58 R08: 0000000000000001 R09: 0000000000000000
[ 360.560206] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ba8ad470
[ 360.560213] R13: 00007f2411bfa000 R14: 0000000000000000 R15: ffff880581ee3fd0
[ 360.560222] FS: 00007f2412de6700(0000) GS:ffff8801de000000(0000) knlGS:0000000000000000
[ 360.560228] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 360.560234] CR2: ffff880581ee3fd0 CR3: 00000001ba89b000 CR4: 00000000000006a0
[ 360.560255] DR0: 00000000006ec000 DR1: 0000000000000000 DR2: 0000000000000000
[ 360.560262] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 00000000000d0602
[ 360.560264] Stack:
[ 360.560278] 0000000000000001 0000000000000000 ffff880581ee4030 ffff880592deaa30
[ 360.560290] 0000000000000005 00007f2411c07000 ffff8801ba8d5a90 ffff880592deaa30
[ 360.560297] 0000000000000000 000000a8ba84b038 000000000000000c 00007f2411c06220
[ 360.560299] Call Trace:
[ 360.560317] ? __rcu_read_unlock (kernel/rcu/update.c:101)
[ 360.560332] handle_mm_fault (mm/memory.c:3092 mm/memory.c:3225 mm/memory.c:3345 mm/memory.c:3374)
[ 360.560345] ? vmacache_update (mm/vmacache.c:61)
[ 360.560358] ? find_vma (mm/mmap.c:2027)
[ 360.560370] __do_page_fault (arch/x86/mm/fault.c:1231)
[ 360.560386] ? context_tracking_user_exit (kernel/context_tracking.c:184)
[ 360.560400] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
[ 360.560413] ? trace_hardirqs_off_caller (kernel/locking/lockdep.c:2639 (discriminator 8))
[ 360.560425] ? trace_hardirqs_off (kernel/locking/lockdep.c:2645)
[ 360.560432] trace_do_page_fault (arch/x86/mm/fault.c:1314 include/linux/jump_label.h:115 include/linux/context_tracking_state.h:27 include/linux/context_tracking.h:45 arch/x86/mm/fault.c:1315)
[ 360.560440] do_async_page_fault (arch/x86/kernel/kvm.c:279)
[ 360.560447] async_page_fault (arch/x86/kernel/entry_64.S:1321)
[ 360.560458] Code: 47 f9 48 8b 8d 68 ff ff ff 48 29 f1 48 c1 e9 0c 49 8d 44 08 ff 48 39 c7 48 0f 46 c7 4c 89 ff 48 89 85 60 ff ff ff e8 3e 19 07 00 <49> 83 3f 00 0f 84 8f 00 00 00 49 83 c6 01 4c 39 b5 60 ff ff ff
All code
========
0: 47 f9 rex.RXB stc
2: 48 8b 8d 68 ff ff ff mov -0x98(%rbp),%rcx
9: 48 29 f1 sub %rsi,%rcx
c: 48 c1 e9 0c shr $0xc,%rcx
10: 49 8d 44 08 ff lea -0x1(%r8,%rcx,1),%rax
15: 48 39 c7 cmp %rax,%rdi
18: 48 0f 46 c7 cmovbe %rdi,%rax
1c: 4c 89 ff mov %r15,%rdi
1f: 48 89 85 60 ff ff ff mov %rax,-0xa0(%rbp)
26: e8 3e 19 07 00 callq 0x71969
2b:* 49 83 3f 00 cmpq $0x0,(%r15) <-- trapping instruction
2f: 0f 84 8f 00 00 00 je 0xc4
35: 49 83 c6 01 add $0x1,%r14
39: 4c 39 b5 60 ff ff ff cmp %r14,-0xa0(%rbp)
...

Code starting with the faulting instruction
===========================================
0: 49 83 3f 00 cmpq $0x0,(%r15)
4: 0f 84 8f 00 00 00 je 0x99
a: 49 83 c6 01 add $0x1,%r14
e: 4c 39 b5 60 ff ff ff cmp %r14,-0xa0(%rbp)
...
[ 360.560458] RIP do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898)
[ 360.560458] RSP <ffff8801ba8bbc98>
[ 360.560458] CR2: ffff880581ee3fd0
[ 360.560458] ---[ end trace ccd7cee352be7945 ]---

Thanks,
Sasha
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Next message: Vlastimil Babka: "Re: [PATCH] usb-core: Remove Fix mes in file hcd.c"
Previous message: Hanjun Guo: "[PATCH 19/19] Documentation: ACPI for ARM64"
In reply to: Sasha Levin: "Re: [PATCHv3 1/2] mm: introduce vm_ops->map_pages()"
Next in thread: Konstantin Khlebnikov: "Re: [PATCHv3 1/2] mm: introduce vm_ops->map_pages()"
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