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lib/ll_addr: improve ll_addr_n2a() a bit 

Apart from making the code a bit more compact and efficient, this also
prevents a potential buffer overflow if the passed buffer is really too
small: Although correctly decrementing the size parameter passed to
snprintf, it could become negative which would then wrap since snprintf
uses (unsigned) size_t for the parameter.

Signed-off-by: Phil Sutter <phil@nwl.cc>
This commit is contained in:
Phil Sutter 2016-03-22 19:35:19 +01:00 committed by Stephen Hemminger
parent 7faf1588a7
commit f63ed3e629
1 changed files with 3 additions and 12 deletions
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15
lib/ll_addr.c
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@ -41,18 +41,9 @@ const char *ll_addr_n2a(const unsigned char *addr, int alen, int type, char *buf
if (alen == 16 && type == ARPHRD_TUNNEL6) {
return inet_ntop(AF_INET6, addr, buf, blen);
}
l = 0;
for (i=0; i<alen; i++) {
if (i==0) {
snprintf(buf+l, blen, "%02x", addr[i]);
blen -= 2;
l += 2;
} else {
snprintf(buf+l, blen, ":%02x", addr[i]);
blen -= 3;
l += 3;
}
}
snprintf(buf, blen, "%02x", addr[0]);
for (i = 1, l = 2; i < alen && l < blen; i++, l += 3)
snprintf(buf + l, blen - l, ":%02x", addr[i]);
return buf;
}