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

[Eric Biggers]

On Mon, Nov 27, 2017 at 10:56:46AM -0800, syzbot wrote:
> ==================================================================
> BUG: KASAN: use-after-free in skcipher_request_set_tfm
> include/crypto/skcipher.h:499 [inline]
> BUG: KASAN: use-after-free in crypto_aead_copy_sgl
> crypto/algif_aead.c:85 [inline]
> BUG: KASAN: use-after-free in _aead_recvmsg crypto/algif_aead.c:210 [inline]
> BUG: KASAN: use-after-free in aead_recvmsg+0x1552/0x1970
> crypto/algif_aead.c:313
> Read of size 4 at addr ffff8801c7194e5c by task syzkaller438416/3340
> 
> CPU: 0 PID: 3340 Comm: syzkaller438416 Not tainted 4.14.0-next-20171124+ #51
> 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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
>  skcipher_request_set_tfm include/crypto/skcipher.h:499 [inline]
>  crypto_aead_copy_sgl crypto/algif_aead.c:85 [inline]
>  _aead_recvmsg crypto/algif_aead.c:210 [inline]
>  aead_recvmsg+0x1552/0x1970 crypto/algif_aead.c:313
>  sock_recvmsg_nosec net/socket.c:805 [inline]
>  sock_recvmsg+0xc9/0x110 net/socket.c:812
>  ___sys_recvmsg+0x29b/0x630 net/socket.c:2207
>  __sys_recvmsg+0xe2/0x210 net/socket.c:2252
>  SYSC_recvmsg net/socket.c:2264 [inline]
>  SyS_recvmsg+0x2d/0x50 net/socket.c:2259
>  entry_SYSCALL_64_fastpath+0x1f/0x96

#syz fix: crypto: algif_aead - fix reference counting of null skcipher