4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
commit 199512b1234f09e44d592153ec82b44212b2f0c4 upstream.
If 'p' is 0 for the software Diffie-Hellman implementation, then dh_max_size() returns 0. In the case of KEYCTL_DH_COMPUTE, this causes ZERO_SIZE_PTR to be passed to sg_init_one(), which with CONFIG_DEBUG_SG=y triggers the 'BUG_ON(!virt_addr_valid(buf));' in sg_set_buf().
Fix this by making crypto_dh_decode_key() reject 0 for 'p'. p=0 makes no sense for any DH implementation because 'p' is supposed to be a prime number. Moreover, 'mod 0' is not mathematically defined.
Bug report:
kernel BUG at ./include/linux/scatterlist.h:140! invalid opcode: 0000 [#1] SMP KASAN CPU: 0 PID: 27112 Comm: syz-executor2 Not tainted 4.14.0-rc7-00010-gf5dbb5d0ce32-dirty #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.3-20171021_125229-anatol 04/01/2014 task: ffff88006caac0c0 task.stack: ffff88006c7c8000 RIP: 0010:sg_set_buf include/linux/scatterlist.h:140 [inline] RIP: 0010:sg_init_one+0x1b3/0x240 lib/scatterlist.c:156 RSP: 0018:ffff88006c7cfb08 EFLAGS: 00010216 RAX: 0000000000010000 RBX: ffff88006c7cfe30 RCX: 00000000000064ee RDX: ffffffff81cf64c3 RSI: ffffc90000d72000 RDI: ffffffff92e937e0 RBP: ffff88006c7cfb30 R08: ffffed000d8f9fab R09: ffff88006c7cfd30 R10: 0000000000000005 R11: ffffed000d8f9faa R12: ffff88006c7cfd30 R13: 0000000000000000 R14: 0000000000000010 R15: ffff88006c7cfc50 FS: 00007fce190fa700(0000) GS:ffff88003ea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fffc6b33db8 CR3: 000000003cf64000 CR4: 00000000000006f0 Call Trace: __keyctl_dh_compute+0xa95/0x19b0 security/keys/dh.c:360 keyctl_dh_compute+0xac/0x100 security/keys/dh.c:434 SYSC_keyctl security/keys/keyctl.c:1745 [inline] SyS_keyctl+0x72/0x2c0 security/keys/keyctl.c:1641 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x4585c9 RSP: 002b:00007fce190f9bd8 EFLAGS: 00000216 ORIG_RAX: 00000000000000fa RAX: ffffffffffffffda RBX: 0000000000738020 RCX: 00000000004585c9 RDX: 000000002000d000 RSI: 0000000020000ff4 RDI: 0000000000000017 RBP: 0000000000000046 R08: 0000000020008000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: 00007fff6e610cde R13: 00007fff6e610cdf R14: 00007fce190fa700 R15: 0000000000000000 Code: 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 33 5b 45 89 6c 24 14 41 5c 41 5d 41 5e 41 5f 5d c3 e8 fd 8f 68 ff <0f> 0b e8 f6 8f 68 ff 0f 0b e8 ef 8f 68 ff 0f 0b e8 e8 8f 68 ff 20 RIP: sg_set_buf include/linux/scatterlist.h:140 [inline] RSP: ffff88006c7cfb08 RIP: sg_init_one+0x1b3/0x240 lib/scatterlist.c:156 RSP: ffff88006c7cfb08
Fixes: 802c7f1c84e4 ("crypto: dh - Add DH software implementation") Reviewed-by: Tudor Ambarus tudor.ambarus@microchip.com Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- crypto/dh_helper.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/crypto/dh_helper.c +++ b/crypto/dh_helper.c @@ -90,6 +90,14 @@ int crypto_dh_decode_key(const char *buf params->p = (void *)(ptr + params->key_size); params->g = (void *)(ptr + params->key_size + params->p_size);
+ /* + * Don't permit 'p' to be 0. It's not a prime number, and it's subject + * to corner cases such as 'mod 0' being undefined or + * crypto_kpp_maxsize() returning 0. + */ + if (memchr_inv(params->p, 0, params->p_size) == NULL) + return -EINVAL; + return 0; } EXPORT_SYMBOL_GPL(crypto_dh_decode_key);