[PATCH v1 1/1] s390/crypto: Fix skcipher_walk return code handling in aes_s390

[Harald Freudenberger <freude@linux.ibm.com>]

The return codes from skcipher_walk_virt() were not properly checked
before entering the processing loops in ecb_aes_crypt() and ctr_aes_crypt().
If skcipher_walk_virt() fails, the walk structure may be in an undefined
state, and attempting to process data could lead to incorrect behavior
or accessing uninitialized memory.

Add proper return code checking to ensure correct handling of the walk
initialization and walk advance and eventually return to the caller
with that return code.

Fixes: 7988fb2c03c8 ("crypto: s390/aes - convert to skcipher API")
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Cc: stable@vger.kernel.org # 5.5+
---
 arch/s390/crypto/aes_s390.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/s390/crypto/aes_s390.c b/arch/s390/crypto/aes_s390.c
index 62edc66d5478..366ce22d3623 100644
--- a/arch/s390/crypto/aes_s390.c
+++ b/arch/s390/crypto/aes_s390.c
@@ -129,7 +129,7 @@ static int ecb_aes_crypt(struct skcipher_request *req, unsigned long modifier)
 		return fallback_skcipher_crypt(sctx, req, modifier);
 
 	ret = skcipher_walk_virt(&walk, req, false);
-	while ((nbytes = walk.nbytes) != 0) {
+	while (!ret && ((nbytes = walk.nbytes) != 0)) {
 		/* only use complete blocks */
 		n = nbytes & ~(AES_BLOCK_SIZE - 1);
 		cpacf_km(sctx->fc | modifier, sctx->key,
@@ -233,7 +233,7 @@ static int cbc_aes_crypt(struct skcipher_request *req, unsigned long modifier)
 		return ret;
 	memcpy(param.iv, walk.iv, AES_BLOCK_SIZE);
 	memcpy(param.key, sctx->key, sctx->key_len);
-	while ((nbytes = walk.nbytes) != 0) {
+	while (!ret && ((nbytes = walk.nbytes) != 0)) {
 		/* only use complete blocks */
 		n = nbytes & ~(AES_BLOCK_SIZE - 1);
 		cpacf_kmc(sctx->fc | modifier, &param,
@@ -359,7 +359,7 @@ static int xts_aes_crypt(struct skcipher_request *req, unsigned long modifier)
 	memcpy(xts_param.key + offset, xts_ctx->key, xts_ctx->key_len);
 	memcpy(xts_param.init, pcc_param.xts, 16);
 
-	while ((nbytes = walk.nbytes) != 0) {
+	while (!ret && ((nbytes = walk.nbytes) != 0)) {
 		/* only use complete blocks */
 		n = nbytes & ~(AES_BLOCK_SIZE - 1);
 		cpacf_km(xts_ctx->fc | modifier, xts_param.key + offset,
@@ -487,7 +487,7 @@ static int fullxts_aes_crypt(struct skcipher_request *req,  unsigned long modifi
 	memcpy(fxts_param.tweak, req->iv, AES_BLOCK_SIZE);
 	fxts_param.nap[0] = 0x01; /* initial alpha power (1, little-endian) */
 
-	while ((nbytes = walk.nbytes) != 0) {
+	while (!ret && ((nbytes = walk.nbytes) != 0)) {
 		/* only use complete blocks */
 		n = nbytes & ~(AES_BLOCK_SIZE - 1);
 		cpacf_km(xts_ctx->fc | modifier, fxts_param.key + offset,
@@ -577,7 +577,7 @@ static int ctr_aes_crypt(struct skcipher_request *req)
 	locked = mutex_trylock(&ctrblk_lock);
 
 	ret = skcipher_walk_virt(&walk, req, false);
-	while ((nbytes = walk.nbytes) >= AES_BLOCK_SIZE) {
+	while (!ret && ((nbytes = walk.nbytes) >= AES_BLOCK_SIZE)) {
 		n = AES_BLOCK_SIZE;
 
 		if (nbytes >= 2*AES_BLOCK_SIZE && locked)
@@ -596,7 +596,7 @@ static int ctr_aes_crypt(struct skcipher_request *req)
 	/*
 	 * final block may be < AES_BLOCK_SIZE, copy only nbytes
 	 */
-	if (nbytes) {
+	if (!ret && nbytes) {
 		memset(buf, 0, AES_BLOCK_SIZE);
 		memcpy(buf, walk.src.virt.addr, nbytes);
 		cpacf_kmctr(sctx->fc, sctx->key, buf, buf,
-- 
2.43.0