Re: [PATCH] crypto: ahash - Set using_shash for cloned ahash wrapper over shash

[Eric Biggers]

On Tue, Nov 07, 2023 at 02:37:17AM +0000, Dmitry Safonov wrote:
> The cloned child of ahash that uses shash under the hood should use
> shash helpers (like crypto_shash_setkey()).
> 
> The following panic may be observed on TCP-AO selftests:
> 
> > ==================================================================
> > BUG: KASAN: wild-memory-access in crypto_mod_get+0x1b/0x60
> > Write of size 4 at addr 5d5be0ff5c415e14 by task connect_ipv4/1397
> >
> > CPU: 0 PID: 1397 Comm: connect_ipv4 Tainted: G        W          6.6.0+ #47
> > Call Trace:
> >  <TASK>
> >  dump_stack_lvl+0x46/0x70
> >  kasan_report+0xc3/0xf0
> >  kasan_check_range+0xec/0x190
> >  crypto_mod_get+0x1b/0x60
> >  crypto_spawn_alg+0x53/0x140
> >  crypto_spawn_tfm2+0x13/0x60
> >  hmac_init_tfm+0x25/0x60
> >  crypto_ahash_setkey+0x8b/0x100
> >  tcp_ao_add_cmd+0xe7a/0x1120
> >  do_tcp_setsockopt+0x5ed/0x12a0
> >  do_sock_setsockopt+0x82/0x100
> >  __sys_setsockopt+0xe9/0x160
> >  __x64_sys_setsockopt+0x60/0x70
> >  do_syscall_64+0x3c/0xe0
> >  entry_SYSCALL_64_after_hwframe+0x46/0x4e
> > ==================================================================
> > general protection fault, probably for non-canonical address 0x5d5be0ff5c415e14: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 1397 Comm: connect_ipv4 Tainted: G    B   W          6.6.0+ #47
> > Call Trace:
> >  <TASK>
> >  ? die_addr+0x3c/0xa0
> >  ? exc_general_protection+0x144/0x210
> >  ? asm_exc_general_protection+0x22/0x30
> >  ? add_taint+0x26/0x90
> >  ? crypto_mod_get+0x20/0x60
> >  ? crypto_mod_get+0x1b/0x60
> >  ? ahash_def_finup_done1+0x58/0x80
> >  crypto_spawn_alg+0x53/0x140
> >  crypto_spawn_tfm2+0x13/0x60
> >  hmac_init_tfm+0x25/0x60
> >  crypto_ahash_setkey+0x8b/0x100
> >  tcp_ao_add_cmd+0xe7a/0x1120
> >  do_tcp_setsockopt+0x5ed/0x12a0
> >  do_sock_setsockopt+0x82/0x100
> >  __sys_setsockopt+0xe9/0x160
> >  __x64_sys_setsockopt+0x60/0x70
> >  do_syscall_64+0x3c/0xe0
> >  entry_SYSCALL_64_after_hwframe+0x46/0x4e
> >  </TASK>
> > RIP: 0010:crypto_mod_get+0x20/0x60
> 
> Make sure that the child/clone has using_shash set when parent is
> an shash user.
> 
> Fixes: 2f1f34c1bf7b ("crypto: ahash - optimize performance when wrapping shash")
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
> Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Francesco Ruggeri <fruggeri05@xxxxxxxxx>
> To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Salam Noureddine <noureddine@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
> ---
>  crypto/ahash.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/crypto/ahash.c b/crypto/ahash.c
> index deee55f939dc..80c3e5354711 100644
> --- a/crypto/ahash.c
> +++ b/crypto/ahash.c
> @@ -651,6 +651,7 @@ struct crypto_ahash *crypto_clone_ahash(struct crypto_ahash *hash)
>  			err = PTR_ERR(shash);
>  			goto out_free_nhash;
>  		}
> +		nhash->using_shash = true;
>  		*nctx = shash;
>  		return nhash;
>  	}
> 
> base-commit: be3ca57cfb777ad820c6659d52e60bbdd36bf5ff

Thanks:

Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Note that this bug would have been prevented if crypto_clone_*() were covered by
the crypto self-tests.

- Eric