This part of the code is pretty weird due to suboptimal variable name
choice: 'data', 'len', 'datalen', 'data_len'.
But even without understanding all of it, the code checking 'datalen - 1
>= 0' assumes 'datalen - 1' may actually become negative, which is not
true since it is unsigned. So make 'datalen' a signed integer instead.
Another issue is the check for "data[datalen] != '*'" which will access
unallocated memory if 'strlen(data) == 0'. So make sure 'datalen >= 0'
before using it as array index.
Signed-off-by: Phil Sutter <p...@nwl.cc>
---
src/evaluate.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/evaluate.c b/src/evaluate.c
index 87f5a6d77d485..523eedabe84ac 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -211,8 +211,9 @@ static int expr_evaluate_symbol(struct eval_ctx *ctx,
struct expr **expr)
static int expr_evaluate_string(struct eval_ctx *ctx, struct expr **exprp)
{
struct expr *expr = *exprp;
- unsigned int len = div_round_up(expr->len, BITS_PER_BYTE), datalen;
+ unsigned int len = div_round_up(expr->len, BITS_PER_BYTE);
struct expr *value, *prefix;
+ int datalen;
int data_len = ctx->ectx.len > 0 ? ctx->ectx.len : len + 1;
char data[data_len];
@@ -228,7 +229,8 @@ static int expr_evaluate_string(struct eval_ctx *ctx,
struct expr **exprp)
mpz_export_data(data, expr->value, BYTEORDER_HOST_ENDIAN, len);
datalen = strlen(data) - 1;
- if (data[datalen] != '*') {
+ if (datalen >= 0 &&
+ data[datalen] != '*') {
/* We need to reallocate the constant expression with the right
* expression length to avoid problems on big endian.
*/
--
2.8.2
--
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