Re: WARNING in crypto_wait_for_test

[Stephan Mueller]

Am Dienstag, 8. Dezember 2015, 12:12:27 schrieb Dmitry Vyukov:

Hi Dmitry,

>Hello,
>
>The following program triggers a WARNING in crypto_wait_for_test:
>
>// autogenerated by syzkaller (http://github.com/google/syzkaller)
>#include <syscall.h>
>#include <string.h>
>#include <stdint.h>
>
>int main()
>{
>        long r0 = syscall(SYS_mmap, 0x20000000ul, 0x1000ul, 0x3ul,
>0x32ul, 0xfffffffffffffffful, 0x0ul);
>        long r1 = syscall(SYS_socket, 0x26ul, 0x5ul, 0x0ul, 0, 0, 0);
>        *(uint16_t*)0x20000000 = 0x26;
>        memcpy((void*)0x20000002,
>"\x73\x6b\x63\x69\x70\x68\x65\x72\x00\x00\x00\x00\x00\x00", 14);
>        *(uint32_t*)0x20000010 = 0x1008;
>        *(uint32_t*)0x20000014 = 0x469b167b45d89a6;

The error is triggered by this ^^^^ line. This line sets sockaddr_alg->mask to 
some strange value. I assume that the mask does not allow the crypto API to 
find the test.

Herbert, alg_bind currently blacklists one bit in the mask and type bit array. 
Shouldn't we instead white-list the allowed bits?

>        memcpy((void*)0x20000018,
>"\x63\x74\x72\x28\x64\x65\x73\x33\x5f\x65\x64\x65\x29\x00\x00\x00\x00\x00\x00
>\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
>x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x
>00\x00\x00\x00\x00\x00\x00", 64);
>        long r7 = syscall(SYS_bind, r1, 0x20000000ul, 0x58ul, 0, 0, 0);
>        return 0;
>}
>
>
>------------[ cut here ]------------
>WARNING: CPU: 1 PID: 11087 at crypto/algapi.c:343
>crypto_wait_for_test+0xc4/0xf0()
>Modules linked in:
>CPU: 1 PID: 11087 Comm: a.out Tainted: G        W       4.4.0-rc3+ #151
>Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> 0000000000000001 ffff88006ca07a78 ffffffff82e0f4b8 0000000041b58ab3
> ffffffff87a9a265 ffffffff82e0f406 ffff88003711e080 00000000ffffffff
> ffffffff89913aa0 0000000000000001 0000000000000001 0000000000002b4f
>Call Trace:
> [<     inline     >] __dump_stack lib/dump_stack.c:15
> [<ffffffff82e0f4b8>] dump_stack+0xb2/0xfa lib/dump_stack.c:50
> [<ffffffff81373336>] warn_slowpath_common+0xe6/0x170 kernel/panic.c:460
> [<ffffffff81373589>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493
> [<ffffffff82ba29e4>] crypto_wait_for_test+0xc4/0xf0 crypto/algapi.c:343
> [<ffffffff82ba2d20>] crypto_register_instance+0x220/0x350
>crypto/algapi.c:558 [<ffffffff82ba9564>]
>crypto_givcipher_default+0x4f4/0x620
>crypto/ablkcipher.c:601
> [<ffffffff82ba984a>] crypto_lookup_skcipher+0x1ba/0x2f0
>crypto/ablkcipher.c:658 [<ffffffff82ba9aae>]
>crypto_alloc_ablkcipher+0x5e/0x1f0 crypto/ablkcipher.c:693
>[<ffffffff82d2a875>] skcipher_bind+0x25/0x30 crypto/algif_skcipher.c:754
>[<ffffffff82d28129>] alg_bind+0x1a9/0x410 crypto/af_alg.c:155
> [<ffffffff856b3a6a>] SYSC_bind+0x20a/0x2c0 net/socket.c:1383
> [<ffffffff856b70f4>] SyS_bind+0x24/0x30 net/socket.c:1369
> [<ffffffff86a89fb6>] entry_SYSCALL_64_fastpath+0x16/0x7a
>arch/x86/entry/entry_64.S:185
>---[ end trace 49f86739a736fa2b ]---
>
>
>strace:
>socket(PF_ALG, SOCK_SEQPACKET, 0)       = 3
>bind(3, {sa_family=AF_ALG, sa_data="skcipher\0\0\0\0\0\0"}, 88) = -1
>ENOENT (No such file or directory)
>
>
>On commit 31ade3b83e1821da5fbb2f11b5b3d4ab2ec39db8 (Nov 29).
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Ciao
Stephan
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