Fix af_alg_alloc_areq() to initialise areq->first_rsgl.sgl.sgt.sgl to point
to the scatterlist array in areq->first_rsgl.sgl.sgl.
Without this, the gcm-aes-s390 driver will oops when it tries to do
gcm_walk_start() on req->dst because req->dst is set to the value of
areq->first_rsgl.sgl.sgl by _aead_recvmsg() calling
aead_request_set_crypt().
The problem comes if an empty ciphertext is passed: the loop in
af_alg_get_rsgl() just passes straight out and doesn't set areq->first_rsgl
up.
This isn't a problem on x86_64 using gcmaes_crypt_by_sg() because, as far
as I can tell, that ignores req->dst and only uses req->src[*].
[*] Is this a bug in aesni-intel_glue.c?
The s390x oops looks something like:
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0000000a00000000 TEID: 0000000a00000803
Fault in home space mode while using kernel ASCE.
AS:00000000a43a0007 R3:0000000000000024
Oops: 003b ilc:2 [#1] SMP
...
Call Trace:
[<000003ff7fc3d47e>] gcm_walk_start+0x16/0x28 [aes_s390]
[<00000000a2a342f2>] crypto_aead_decrypt+0x9a/0xb8
[<00000000a2a60888>] aead_recvmsg+0x478/0x698
[<00000000a2e519a0>] sock_recvmsg+0x70/0xb0
[<00000000a2e51a56>] sock_read_iter+0x76/0xa0
[<00000000a273e066>] vfs_read+0x26e/0x2a8
[<00000000a273e8c4>] ksys_read+0xbc/0x100
[<00000000a311d808>] __do_syscall+0x1d0/0x1f8
[<00000000a312ff30>] system_call+0x70/0x98
Last Breaking-Event-Address:
[<000003ff7fc3e6b4>] gcm_aes_crypt+0x104/0xa68 [aes_s390]
Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create scatterlists")
Reported-by: Ondrej Mosnáček <omosnacek@xxxxxxxxx>
Link: https://lore.kernel.org/r/CAAUqJDuRkHE8fPgZJGaKjUjd3QfGwzfumuJBmStPqBhubxyk_A@xxxxxxxxxxxxxx/
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
cc: Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx>
cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
cc: Paolo Abeni <pabeni@xxxxxxxxxx>
cc: linux-crypto@xxxxxxxxxxxxxxx
cc: linux-s390@xxxxxxxxxxxxxxx
cc: regressions@xxxxxxxxxxxxxxx
---
crypto/af_alg.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 06b15b9f661c..9ee8575d3b1a 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1192,6 +1192,7 @@ struct af_alg_async_req *af_alg_alloc_areq(struct sock *sk,
areq->areqlen = areqlen;
areq->sk = sk;
+ areq->first_rsgl.sgl.sgt.sgl = areq->first_rsgl.sgl.sgl;
areq->last_rsgl = NULL;
INIT_LIST_HEAD(&areq->rsgl_list);
areq->tsgl = NULL;
