[PATCH] crypto: qat - avoid OOB read when stripping RSA leading zeros

The logical AND operator uses short-circuit evaluation: the first
operand is always evaluated, while the second is evaluated only if
the first is true. Because the first operand dereferences a pointer,
it may cause an out-of-bounds access before the bounds check in the
second operand is evaluated.

Resolve this by checking the vlen prior to the pointer being dereferenced.

Fixes: a990532023b9 ("crypto: qat - Add support for RSA algorithm")
Signed-off-by: Ahsan Atta <[email protected]>
Reviewed-by: Giovanni Cabiddu <[email protected]>
---
 drivers/crypto/intel/qat/qat_common/qat_asym_algs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/intel/qat/qat_common/qat_asym_algs.c b/drivers/crypto/intel/qat/qat_common/qat_asym_algs.c
index 75c15c8e41db..aa2ea563f25f 100644
--- a/drivers/crypto/intel/qat/qat_common/qat_asym_algs.c
+++ b/drivers/crypto/intel/qat/qat_common/qat_asym_algs.c
@@ -987,7 +987,7 @@ static int qat_rsa_set_n(struct qat_rsa_ctx *ctx, const char *value,
 	const char *ptr = value;
 	int ret;
 
-	while (!*ptr && vlen) {
+	while (vlen && !*ptr) {
 		ptr++;
 		vlen--;
 	}
@@ -1018,7 +1018,7 @@ static int qat_rsa_set_e(struct qat_rsa_ctx *ctx, const char *value,
 	struct device *dev = &GET_DEV(inst->accel_dev);
 	const char *ptr = value;
 
-	while (!*ptr && vlen) {
+	while (vlen && !*ptr) {
 		ptr++;
 		vlen--;
 	}
@@ -1044,7 +1044,7 @@ static int qat_rsa_set_d(struct qat_rsa_ctx *ctx, const char *value,
 	const char *ptr = value;
 	int ret;
 
-	while (!*ptr && vlen) {
+	while (vlen && !*ptr) {
 		ptr++;
 		vlen--;
 	}
@@ -1067,7 +1067,7 @@ static int qat_rsa_set_d(struct qat_rsa_ctx *ctx, const char *value,
 
 static void qat_rsa_drop_leading_zeros(const char **ptr, unsigned int *len)
 {
-	while (!**ptr && *len) {
+	while (*len && !**ptr) {
 		(*ptr)++;
 		(*len)--;
 	}
-- 
2.50.1

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