Re: KASAN: use-after-free Read in crypto_aead_free_instance

[Dmitry Vyukov]

On Wed, Dec 20, 2017 at 10:17 AM, Stephan MÃller <smueller@xxxxxxxxxx> wrote:
> Am Mittwoch, 20. Dezember 2017, 08:48:01 CET schrieb syzbot:
>
> Hi,
>
>> Hello,
>>
>> syzkaller hit the following crash on
>> 032b4cc8ff84490c4bc7c4ef8c91e6d83a637538
>> 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.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>>
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in crypto_aead_free_instance+0xc0/0xd0
>> crypto/aead.c:154
>> Read of size 8 at addr ffff8801c32cf240 by task cryptomgr_test/6646
>>
>> CPU: 1 PID: 6646 Comm: cryptomgr_test Not tainted 4.15.0-rc3+ #132
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>   __dump_stack lib/dump_stack.c:17 [inline]
>>   dump_stack+0x194/0x257 lib/dump_stack.c:53
>>   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
>>   crypto_aead_free_instance+0xc0/0xd0 crypto/aead.c:154
>>   crypto_free_instance+0x6d/0x100 crypto/algapi.c:77
>>   crypto_destroy_instance+0x3c/0x80 crypto/algapi.c:85
>>   crypto_alg_put crypto/internal.h:116 [inline]
>>   crypto_remove_final+0x212/0x370 crypto/algapi.c:331
>>   crypto_alg_tested+0x445/0x6f0 crypto/algapi.c:320
>>   cryptomgr_test+0x17/0x30 crypto/algboss.c:226
>>   kthread+0x37a/0x440 kernel/kthread.c:238
>>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441
>>
>> Allocated by task 6641:
>>   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
>>   kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
>>   kmalloc include/linux/slab.h:499 [inline]
>>   kzalloc include/linux/slab.h:688 [inline]
>>   pcrypt_create_aead crypto/pcrypt.c:291 [inline]
>>   pcrypt_create+0x137/0x6c0 crypto/pcrypt.c:346
>>   cryptomgr_probe+0x74/0x240 crypto/algboss.c:75
>>   kthread+0x37a/0x440 kernel/kthread.c:238
>>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441
>>
>> Freed by task 3335:
>>   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:3488 [inline]
>>   kfree+0xca/0x250 mm/slab.c:3803
>>   crypto_larval_destroy+0x110/0x150 crypto/api.c:107
>>   crypto_alg_put crypto/internal.h:116 [inline]
>>   crypto_larval_kill+0x1e8/0x2e0 crypto/api.c:167
>>   crypto_alg_mod_lookup+0x178/0x1b0 crypto/api.c:283
>>   crypto_find_alg crypto/api.c:501 [inline]
>>   crypto_alloc_tfm+0xf3/0x2f0 crypto/api.c:534
>>   crypto_alloc_aead+0x2c/0x40 crypto/aead.c:342
>>   aead_bind+0x70/0x140 crypto/algif_aead.c:482
>>   alg_bind+0x1ab/0x440 crypto/af_alg.c:179
>>   SYSC_bind+0x1b4/0x3f0 net/socket.c:1454
>>   SyS_bind+0x24/0x30 net/socket.c:1440
>>   do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
>>   do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
>>   entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
>>
> This issue vanishes after applying the patch "[PATCH v2] crypto: AF_ALG -
> limit mask and type".


Hi Stephan,

syzbot does not understand arbitrary English prose, it only understands this:

> Once a fix for this bug is merged into any tree, reply to this email with:
> #syz fix: exact-commit-title

Let's tell it about the fix:

#syz fix: crypto: AF_ALG - limit mask and type