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-rw-r--r--libc/inet/ether_addr.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/libc/inet/ether_addr.c b/libc/inet/ether_addr.c
index 621c62989..9071d71de 100644
--- a/libc/inet/ether_addr.c
+++ b/libc/inet/ether_addr.c
@@ -38,10 +38,12 @@ struct ether_addr *ether_aton_r(const char *asc, struct ether_addr *addr)
for (cnt = 0; cnt < 6; ++cnt) {
unsigned char number;
- char ch;
+ char ch = *asc++;
+ if (ch < 0x20)
+ return NULL;
/* | 0x20 is cheap tolower(), valid for letters/numbers only */
- ch = (*asc++) | 0x20;
+ ch |= 0x20;
if ((ch < '0' || ch > '9') && (ch < 'a' || ch > 'f'))
return NULL;
number = !(ch > '9') ? (ch - '0') : (ch - 'a' + 10);