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Date:   Tue, 31 Mar 2020 12:35:13 -0700
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Subject: KCSAN: data-race in glue_cbc_decrypt_req_128bit / glue_cbc_decrypt_req_128bit
From:   syzbot <syzbot+6a6bca8169ffda8ce77b@syzkaller.appspotmail.com>
To:     bp@alien8.de, davem@davemloft.net, elver@google.com,
        herbert@gondor.apana.org.au, hpa@zytor.com,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
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Hello,

syzbot found the following crash on:

HEAD commit:    b12d66a6 mm, kcsan: Instrument SLAB free with ASSERT_EXCLU..
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=111f0865e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=10bc0131c4924ba9
dashboard link: https://syzkaller.appspot.com/bug?extid=6a6bca8169ffda8ce77b
compiler:       gcc (GCC) 9.0.0 20181231 (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+6a6bca8169ffda8ce77b@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in glue_cbc_decrypt_req_128bit / glue_cbc_decrypt_req_128bit

write to 0xffff88809966e128 of 8 bytes by task 24119 on cpu 0:
 u128_xor include/crypto/b128ops.h:67 [inline]
 glue_cbc_decrypt_req_128bit+0x396/0x460 arch/x86/crypto/glue_helper.c:144
 cbc_decrypt+0x26/0x40 arch/x86/crypto/serpent_avx2_glue.c:152
 crypto_skcipher_decrypt+0x65/0x90 crypto/skcipher.c:652
 _skcipher_recvmsg crypto/algif_skcipher.c:142 [inline]
 skcipher_recvmsg+0x7fa/0x8c0 crypto/algif_skcipher.c:161
 skcipher_recvmsg_nokey+0x5e/0x80 crypto/algif_skcipher.c:279
 sock_recvmsg_nosec net/socket.c:886 [inline]
 sock_recvmsg net/socket.c:904 [inline]
 sock_recvmsg+0x92/0xb0 net/socket.c:900
 ____sys_recvmsg+0x167/0x3a0 net/socket.c:2566
 ___sys_recvmsg+0xb2/0x100 net/socket.c:2608
 __sys_recvmsg+0x9d/0x160 net/socket.c:2642
 __do_sys_recvmsg net/socket.c:2652 [inline]
 __se_sys_recvmsg net/socket.c:2649 [inline]
 __x64_sys_recvmsg+0x51/0x70 net/socket.c:2649
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809966e128 of 8 bytes by task 24118 on cpu 1:
 u128_xor include/crypto/b128ops.h:67 [inline]
 glue_cbc_decrypt_req_128bit+0x37c/0x460 arch/x86/crypto/glue_helper.c:144
 cbc_decrypt+0x26/0x40 arch/x86/crypto/serpent_avx2_glue.c:152
 crypto_skcipher_decrypt+0x65/0x90 crypto/skcipher.c:652
 _skcipher_recvmsg crypto/algif_skcipher.c:142 [inline]
 skcipher_recvmsg+0x7fa/0x8c0 crypto/algif_skcipher.c:161
 skcipher_recvmsg_nokey+0x5e/0x80 crypto/algif_skcipher.c:279
 sock_recvmsg_nosec net/socket.c:886 [inline]
 sock_recvmsg net/socket.c:904 [inline]
 sock_recvmsg+0x92/0xb0 net/socket.c:900
 ____sys_recvmsg+0x167/0x3a0 net/socket.c:2566
 ___sys_recvmsg+0xb2/0x100 net/socket.c:2608
 __sys_recvmsg+0x9d/0x160 net/socket.c:2642
 __do_sys_recvmsg net/socket.c:2652 [inline]
 __se_sys_recvmsg net/socket.c:2649 [inline]
 __x64_sys_recvmsg+0x51/0x70 net/socket.c:2649
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24118 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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