[syzbot] [crypto?] BUG: unable to handle kernel NULL pointer dereference in crypto_arc4_crypt

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3a5879d495b2 Merge tag 'ata-6.8-rc2' of git://git.kernel.o..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1683b6bbe80000
kernel config: https://syzkaller.appspot.com/x/.config?x=bc36d99546fe9035
dashboard link: https://syzkaller.appspot.com/bug?extid=050eeedd6c285d8c42f2
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15178ea0180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107f8eefe80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6f5df0cd5c86/disk-3a5879d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/284ff9c3970b/vmlinux-3a5879d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b75c80c77fad/bzImage-3a5879d4.xz

The issue was bisected to:

commit 47309ea1359115125d9cab17a279c8df72b47235
Author: Herbert Xu <her...@gondor.apana.org.au>
Date: Tue Nov 28 06:52:57 2023 +0000

crypto: arc4 - Add internal state

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1325e5a0180000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10a5e5a0180000
console output: https://syzkaller.appspot.com/x/log.txt?x=1725e5a0180000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+050eee...@syzkaller.appspotmail.com
Fixes: 47309ea13591 ("crypto: arc4 - Add internal state")

"syz-executor299" (5065) uses obsolete ecb(arc4) skcipher
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 78051067 P4D 78051067 PUD 7e3d7067 PMD 0
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5065 Comm: syz-executor299 Not tainted 6.8.0-rc1-syzkaller-00311-g3a5879d495b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:memcpy_orig+0x31/0x120 arch/x86/lib/memcpy_64.S:71
Code: 48 83 fa 20 0f 82 86 00 00 00 40 38 fe 7c 35 48 83 ea 20 48 83 ea 20 4c 8b 06 4c 8b 4e 08 4c 8b 56 10 4c 8b 5e 18 48 8d 76 20 <4c> 89 07 4c 89 4f 08 4c 89 57 10 4c 89 5f 18 48 8d 7f 20 73 d4 83
RSP: 0018:ffffc90003a378c0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff84401c81
RDX: 00000000000003c8 RSI: ffff888019ee1040 RDI: 0000000000000000
RBP: ffff888019ee1000 R08: 0000000400000003 R09: 0000002200000071
R10: 0000000800000016 R11: 0000001700000083 R12: 0000000000000000
R13: ffff88807f225da0 R14: ffff88807929e000 R15: 0000000000000001
FS: 00005555570b8380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007c30c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
crypto_arc4_crypt+0x4b/0x70 crypto/arc4.c:33
crypto_lskcipher_crypt crypto/lskcipher.c:160 [inline]
crypto_lskcipher_decrypt+0xd4/0x130 crypto/lskcipher.c:194
crypto_cbc_decrypt_segment crypto/cbc.c:80 [inline]
crypto_cbc_decrypt+0x14f/0x330 crypto/cbc.c:133
crypto_lskcipher_crypt_sg+0x28c/0x460 crypto/lskcipher.c:229
crypto_skcipher_decrypt+0xda/0x160 crypto/skcipher.c:693
_skcipher_recvmsg crypto/algif_skcipher.c:199 [inline]
skcipher_recvmsg+0xc2b/0x1040 crypto/algif_skcipher.c:221
sock_recvmsg_nosec net/socket.c:1046 [inline]
sock_recvmsg+0xe2/0x170 net/socket.c:1068
__sys_recvfrom+0x1ab/0x2e0 net/socket.c:2242
__do_sys_recvfrom net/socket.c:2260 [inline]
__se_sys_recvfrom net/socket.c:2256 [inline]
__x64_sys_recvfrom+0xe0/0x1b0 net/socket.c:2256
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd3/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f23399079b9
Code: ff e8 cb 01 00 00 66 2e 0f 1f 84 00 00 00 00 00 90 80 3d f1 56 07 00 00 41 89 ca 74 1c 45 31 c9 45 31 c0 b8 2d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 67 c3 66 0f 1f 44 00 00 55 48 83 ec 20 48 89
RSP: 002b:00007ffe68b37d28 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007ffe68b37db4 RCX: 00007f23399079b9
RDX: 0000000000001000 RSI: 00007ffe68b37da0 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe68b37da0
R13: 00007ffe68b38f88 R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:memcpy_orig+0x31/0x120 arch/x86/lib/memcpy_64.S:71
Code: 48 83 fa 20 0f 82 86 00 00 00 40 38 fe 7c 35 48 83 ea 20 48 83 ea 20 4c 8b 06 4c 8b 4e 08 4c 8b 56 10 4c 8b 5e 18 48 8d 76 20 <4c> 89 07 4c 89 4f 08 4c 89 57 10 4c 89 5f 18 48 8d 7f 20 73 d4 83
RSP: 0018:ffffc90003a378c0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff84401c81
RDX: 00000000000003c8 RSI: ffff888019ee1040 RDI: 0000000000000000
RBP: ffff888019ee1000 R08: 0000000400000003 R09: 0000002200000071
R10: 0000000800000016 R11: 0000001700000083 R12: 0000000000000000
R13: ffff88807f225da0 R14: ffff88807929e000 R15: 0000000000000001
FS: 00005555570b8380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007c30c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 48 83 fa 20 cmp $0x20,%rdx
4: 0f 82 86 00 00 00 jb 0x90
a: 40 38 fe cmp %dil,%sil
d: 7c 35 jl 0x44
f: 48 83 ea 20 sub $0x20,%rdx
13: 48 83 ea 20 sub $0x20,%rdx
17: 4c 8b 06 mov (%rsi),%r8
1a: 4c 8b 4e 08 mov 0x8(%rsi),%r9
1e: 4c 8b 56 10 mov 0x10(%rsi),%r10
22: 4c 8b 5e 18 mov 0x18(%rsi),%r11
26: 48 8d 76 20 lea 0x20(%rsi),%rsi
* 2a: 4c 89 07 mov %r8,(%rdi) <-- trapping instruction
2d: 4c 89 4f 08 mov %r9,0x8(%rdi)
31: 4c 89 57 10 mov %r10,0x10(%rdi)
35: 4c 89 5f 18 mov %r11,0x18(%rdi)
39: 48 8d 7f 20 lea 0x20(%rdi),%rdi
3d: 73 d4 jae 0x13
3f: 83 .byte 0x83


---
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[Herbert Xu]

On Mon, Jan 29, 2024 at 04:55:30AM -0800, syzbot wrote:
>
> HEAD commit: 3a5879d495b2 Merge tag 'ata-6.8-rc2' of git://git.kernel.o..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1683b6bbe80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=bc36d99546fe9035
> dashboard link: https://syzkaller.appspot.com/bug?extid=050eeedd6c285d8c42f2

Thanks for the report. This is actually caused by the construction
of cbc(arc4), which wasn't possible previously. Let's make it
impossible again:

---8<---
The cbc template should not be applied on stream ciphers, especially
ones that have internal state. Enforce this by checking the state
size when the instance is created.

Reported-by: syzbot+050eee...@syzkaller.appspotmail.com
Fixes: 47309ea13591 ("crypto: arc4 - Add internal state")

Signed-off-by: Herbert Xu <her...@gondor.apana.org.au>

diff --git a/crypto/cbc.c b/crypto/cbc.c
index eedddef9ce40..e81918ca68b7 100644
--- a/crypto/cbc.c
+++ b/crypto/cbc.c
@@ -148,6 +148,9 @@ static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
if (!is_power_of_2(inst->alg.co.base.cra_blocksize))
goto out_free_inst;

+ if (inst->alg.co.statesize)
+ goto out_free_inst;
+
inst->alg.encrypt = crypto_cbc_encrypt;
inst->alg.decrypt = crypto_cbc_decrypt;

--
Email: Herbert Xu <her...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt