linux-kernel - Re: KASAN: use-after-free Read in crypto_destroy

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Date:   Tue, 29 May 2018 11:21:15 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+352126a5be7ccb25754e@...kaller.appspotmail.com>,
        Eric Biggers <ebiggers@...gle.com>,
        David Miller <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in crypto_destroy_tfm

On Sat, May 26, 2018 at 07:41:34PM +0200, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Sat, May 26, 2018 at 7:40 PM, syzbot
> <syzbot+352126a5be7ccb25754e@...kaller.appspotmail.com> wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    0644f186fc9d Merge tag 'for_linus' of git://git.kernel.org..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=102bc257800000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=61c12b53c2a25ec4
> > dashboard link: https://syzkaller.appspot.com/bug?extid=352126a5be7ccb25754e
> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+352126a5be7ccb25754e@...kaller.appspotmail.com
> 
> Eric, do you remember if we had any recent fixes for this?

I don't think so.  Commit eea0d3ea754696 ("crypto: drbg - set freed buffers to
NULL") *might* be related, but this looks different.

> 
> > ==================================================================
> > BUG: KASAN: use-after-free in crypto_destroy_tfm+0x2a3/0x300
> > crypto/api.c:573
> > Read of size 8 at addr ffff8801d9023238 by task syz-executor6/10078
> >
> > CPU: 1 PID: 10078 Comm: syz-executor6 Not tainted 4.17.0-rc2+ #19
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
> >  print_address_description+0x6c/0x20b mm/kasan/report.c:256
> >  kasan_report_error mm/kasan/report.c:354 [inline]
> >  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
> >  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
> >  crypto_destroy_tfm+0x2a3/0x300 crypto/api.c:573
> >  crypto_free_rng include/crypto/rng.h:122 [inline]
> >  rng_release+0x18/0x20 crypto/algif_rng.c:124
> >  alg_do_release crypto/af_alg.c:119 [inline]
> >  alg_sock_destruct+0x92/0xe0 crypto/af_alg.c:362
> >  __sk_destruct+0xff/0xa40 net/core/sock.c:1566
> >  sk_destruct+0x78/0x90 net/core/sock.c:1601
> >  __sk_free+0x22e/0x340 net/core/sock.c:1612
> >  sk_free+0x42/0x50 net/core/sock.c:1623
> >  sock_put include/net/sock.h:1664 [inline]
> >  af_alg_release+0x6e/0x90 crypto/af_alg.c:126
> >  sock_release+0x96/0x1b0 net/socket.c:594
> >  sock_close+0x16/0x20 net/socket.c:1149
> >  __fput+0x34d/0x890 fs/file_table.c:209
> >  ____fput+0x15/0x20 fs/file_table.c:243
> >  task_work_run+0x1e4/0x290 kernel/task_work.c:113
> >  exit_task_work include/linux/task_work.h:22 [inline]
> >  do_exit+0x1aee/0x2730 kernel/exit.c:865
> >  do_group_exit+0x16f/0x430 kernel/exit.c:968
> >  get_signal+0x886/0x1960 kernel/signal.c:2469
> >  do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
> >  exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
> >  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
> >  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
> >  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
> >  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x455979
> > RSP: 002b:00007f4f4bbc2c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> > RAX: 0000000000000000 RBX: 00007f4f4bbc36d4 RCX: 0000000000455979
> > RDX: 0000000000000001 RSI: 0000000000000117 RDI: 0000000000000014
> > RBP: 000000000072bf50 R08: 0000000000000000 R09: 0000000000000000
> > R10: 00000000204f7000 R11: 0000000000000246 R12: 00000000ffffffff
> > R13: 0000000000000519 R14: 00000000006faaf8 R15: 0000000000000001
> >
> > Allocated by task 4484:
> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> >  set_track mm/kasan/kasan.c:460 [inline]
> >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
> >  __do_kmalloc_node mm/slab.c:3682 [inline]
> >  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696
> >  __kmalloc_reserve.isra.38+0x3a/0xe0 net/core/skbuff.c:137
> >  __alloc_skb+0x14d/0x780 net/core/skbuff.c:205
> >  alloc_skb include/linux/skbuff.h:987 [inline]
> >  netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
> >  netlink_sendmsg+0xb01/0xfa0 net/netlink/af_netlink.c:1876
> >  sock_sendmsg_nosec net/socket.c:629 [inline]
> >  sock_sendmsg+0xd5/0x120 net/socket.c:639
> >  ___sys_sendmsg+0x805/0x940 net/socket.c:2117
> >  __sys_sendmsg+0x115/0x270 net/socket.c:2155
> >  __do_sys_sendmsg net/socket.c:2164 [inline]
> >  __se_sys_sendmsg net/socket.c:2162 [inline]
> >  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
> >  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
> >  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > Freed by task 4484:
> >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
> >  set_track mm/kasan/kasan.c:460 [inline]
> >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
> >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
> >  __cache_free mm/slab.c:3498 [inline]
> >  kfree+0xd9/0x260 mm/slab.c:3813
> >  skb_free_head+0x99/0xc0 net/core/skbuff.c:550
> >  skb_release_data+0x690/0x860 net/core/skbuff.c:570
> >  skb_release_all+0x4a/0x60 net/core/skbuff.c:627
> >  __kfree_skb net/core/skbuff.c:641 [inline]
> >  consume_skb+0x18b/0x550 net/core/skbuff.c:701
> >  netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
> >  netlink_unicast+0x593/0x740 net/netlink/af_netlink.c:1336
> >  netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
> >  sock_sendmsg_nosec net/socket.c:629 [inline]
> >  sock_sendmsg+0xd5/0x120 net/socket.c:639
> >  ___sys_sendmsg+0x805/0x940 net/socket.c:2117
> >  __sys_sendmsg+0x115/0x270 net/socket.c:2155
> >  __do_sys_sendmsg net/socket.c:2164 [inline]
> >  __se_sys_sendmsg net/socket.c:2162 [inline]
> >  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
> >  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
> >  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > The buggy address belongs to the object at ffff8801d9023200
> >  which belongs to the cache kmalloc-1024 of size 1024
> > The buggy address is located 56 bytes inside of
> >  1024-byte region [ffff8801d9023200, ffff8801d9023600)
> > The buggy address belongs to the page:
> > page:ffffea0007640880 count:1 mapcount:0 mapping:ffff8801d9022000 index:0x0
> > compound_mapcount: 0
> > flags: 0x2fffc0000008100(slab|head)
> > raw: 02fffc0000008100 ffff8801d9022000 0000000000000000 0000000100000007
> > raw: ffffea0006ea5e20 ffffea00073785a0 ffff8801da800ac0 0000000000000000
> > page dumped because: kasan: bad access detected
> >
> > Memory state around the buggy address:
> >  ffff8801d9023100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff8801d9023180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >>
> >> ffff8801d9023200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >
> >                                         ^
> >  ffff8801d9023280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  ffff8801d9023300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ==================================================================
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@...glegroups.com.
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> > syzbot.
> >
> > --
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