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dns_compare_name: change check for u16_t overflow

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check upper border (0xFFFF) instead of checking for 0 after overflow
This commit is contained in:
goldsimon 2018-02-13 12:23:50 +01:00
parent d4047ea1d1
commit bcb6819715
1 changed files with 8 additions and 4 deletions
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12
src/core/dns.c
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@ -649,10 +649,12 @@ dns_compare_name(const char *query, struct pbuf *p, u16_t start_offset)
u16_t response_offset = start_offset;
do {
n = pbuf_try_get_at(p, response_offset++);
if ((n < 0) || (response_offset == 0)) {
n = pbuf_try_get_at(p, response_offset);
if ((n < 0) || (response_offset == 0xFFFF)) {
/* error or overflow */
return 0xFFFF;
}
response_offset++;
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name: cannot be equal since we don't send them */
@ -667,10 +669,11 @@ dns_compare_name(const char *query, struct pbuf *p, u16_t start_offset)
if ((*query) != (u8_t)c) {
return 0xFFFF;
}
++response_offset;
if (response_offset == 0) {
if (response_offset == 0xFFFF) {
/* would overflow */
return 0xFFFF;
}
response_offset++;
++query;
--n;
}
@ -683,6 +686,7 @@ dns_compare_name(const char *query, struct pbuf *p, u16_t start_offset)
} while (n != 0);
if (response_offset == 0xFFFF) {
/* would overflow */
return 0xFFFF;
}
return (u16_t)(response_offset + 1);