Re: [PATCH v2 0/9] kasan: improve error reports

[Dmitry Vyukov]

On Thu, Mar 2, 2017 at 2:48 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> This patchset improves KASAN reports by making them easier to read
> and a little more detailed.
> Also improves mm/kasan/report.c readability.

Acked-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

> Effectively changes a use-after-free report to:
>
> ==================================================================
> BUG: KASAN: use-after-free in kmalloc_uaf+0xaa/0xb6 [test_kasan]
> Write of size 1 at addr ffff88006aa59da8 by task insmod/3951
>
> CPU: 1 PID: 3951 Comm: insmod Tainted: G    B           4.10.0+ #84
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  dump_stack+0x292/0x398
>  print_address_description+0x73/0x280
>  kasan_report.part.2+0x207/0x2f0
>  __asan_report_store1_noabort+0x2c/0x30
>  kmalloc_uaf+0xaa/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x7f22cfd0b9da
> RSP: 002b:00007ffe69118a78 EFLAGS: 00000206 ORIG_RAX: 00000000000000af
> RAX: ffffffffffffffda RBX: 0000555671242090 RCX: 00007f22cfd0b9da
> RDX: 00007f22cffcaf88 RSI: 000000000004df7e RDI: 00007f22d0399000
> RBP: 00007f22cffcaf88 R08: 0000000000000003 R09: 0000000000000000
> R10: 00007f22cfd07d0a R11: 0000000000000206 R12: 0000555671243190
> R13: 000000000001fe81 R14: 0000000000000000 R15: 0000000000000004
>
> Allocated by task 3951:
>  save_stack_trace+0x16/0x20
>  save_stack+0x43/0xd0
>  kasan_kmalloc+0xad/0xe0
>  kmem_cache_alloc_trace+0x82/0x270
>  kmalloc_uaf+0x56/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
>
> Freed by task 3951:
>  save_stack_trace+0x16/0x20
>  save_stack+0x43/0xd0
>  kasan_slab_free+0x72/0xc0
>  kfree+0xe8/0x2b0
>  kmalloc_uaf+0x85/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc
>
> The buggy address belongs to the object at ffff88006aa59da0
>  which belongs to the cache kmalloc-16 of size 16
> The buggy address is located 8 bytes inside of
>  16-byte region [ffff88006aa59da0, ffff88006aa59db0)
> The buggy address belongs to the page:
> page:ffffea0001aa9640 count:1 mapcount:0 mapping:          (null) index:0x0
> flags: 0x100000000000100(slab)
> raw: 0100000000000100 0000000000000000 0000000000000000 0000000180800080
> raw: ffffea0001abe380 0000000700000007 ffff88006c401b40 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff88006aa59c80: 00 00 fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
>  ffff88006aa59d00: 00 00 fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
>>ffff88006aa59d80: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>                                   ^
>  ffff88006aa59e00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>  ffff88006aa59e80: fb fb fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
> ==================================================================
>
> from:
>
> ==================================================================
> BUG: KASAN: use-after-free in kmalloc_uaf+0xaa/0xb6 [test_kasan] at addr ffff88006c4dcb28
> Write of size 1 by task insmod/3984
> CPU: 1 PID: 3984 Comm: insmod Tainted: G    B           4.10.0+ #83
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  dump_stack+0x292/0x398
>  kasan_object_err+0x1c/0x70
>  kasan_report.part.1+0x20e/0x4e0
>  __asan_report_store1_noabort+0x2c/0x30
>  kmalloc_uaf+0xaa/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x7feca0f779da
> RSP: 002b:00007ffdfeae5218 EFLAGS: 00000206 ORIG_RAX: 00000000000000af
> RAX: ffffffffffffffda RBX: 000055a064c13090 RCX: 00007feca0f779da
> RDX: 00007feca1236f88 RSI: 000000000004df7e RDI: 00007feca1605000
> RBP: 00007feca1236f88 R08: 0000000000000003 R09: 0000000000000000
> R10: 00007feca0f73d0a R11: 0000000000000206 R12: 000055a064c14190
> R13: 000000000001fe81 R14: 0000000000000000 R15: 0000000000000004
> Object at ffff88006c4dcb20, in cache kmalloc-16 size: 16
> Allocated:
> PID = 3984
>  save_stack_trace+0x16/0x20
>  save_stack+0x43/0xd0
>  kasan_kmalloc+0xad/0xe0
>  kmem_cache_alloc_trace+0x82/0x270
>  kmalloc_uaf+0x56/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> Freed:
> PID = 3984
>  save_stack_trace+0x16/0x20
>  save_stack+0x43/0xd0
>  kasan_slab_free+0x73/0xc0
>  kfree+0xe8/0x2b0
>  kmalloc_uaf+0x85/0xb6 [test_kasan]
>  kmalloc_tests_init+0x4f/0xa48 [test_kasan]
>  do_one_initcall+0xf3/0x390
>  do_init_module+0x215/0x5d0
>  load_module+0x54de/0x82b0
>  SYSC_init_module+0x3be/0x430
>  SyS_init_module+0x9/0x10
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> Memory state around the buggy address:
>  ffff88006c4dca00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>  ffff88006c4dca80: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>>ffff88006c4dcb00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
>                                   ^
>  ffff88006c4dcb80: fb fb fc fc 00 00 fc fc fb fb fc fc fb fb fc fc
>  ffff88006c4dcc00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
> ==================================================================
>
> Changes in v2:
> - split patch in multiple smaller ones
> - improve double-free reports
>
> Andrey Konovalov (9):
>   kasan: introduce helper functions for determining bug type
>   kasan: unify report headers
>   kasan: change allocation and freeing stack traces headers
>   kasan: simplify address description logic
>   kasan: change report header
>   kasan: improve slab object description
>   kasan: print page description after stacks
>   kasan: improve double-free report format
>   kasan: separate report parts by empty lines
>
>  mm/kasan/kasan.c  |   3 +-
>  mm/kasan/kasan.h  |   2 +-
>  mm/kasan/report.c | 187 ++++++++++++++++++++++++++++++++++++------------------
>  3 files changed, 127 insertions(+), 65 deletions(-)
>
> --
> 2.12.0.rc1.440.g5b76565f74-goog
>