From 21503ed2af233ffe795926f6641ac84ec1b15bf9 Mon Sep 17 00:00:00 2001 From: Michal Kubecek Date: Thu, 19 Oct 2017 10:21:08 +0200 Subject: [PATCH] ip maddr: fix filtering by device Commit 530903dd9003 ("ip: fix igmp parsing when iface is long") uses variable len to keep trailing colon from interface name comparison. This variable is local to loop body but we set it in one pass and use it in following one(s) so that we are actually using (pseudo)random length for comparison. This became apparent since commit b48a1161f5f9 ("ipmaddr: Avoid accessing uninitialized data") always initializes len to zero so that the name comparison is always true. As a result, "ip maddr show dev eth0" shows IPv4 multicast addresses for all interfaces. Instead of keeping the length, let's simply replace the trailing colon with a null byte. The bonus is that we get correct interface name in ma.name. Fixes: 530903dd9003 ("ip: fix igmp parsing when iface is long") Signed-off-by: Michal Kubecek Acked-by: Phil Sutter Acked-by: Petr Vorel --- ip/ipmaddr.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/ip/ipmaddr.c b/ip/ipmaddr.c index 5683f6fa8..46b86a3a7 100644 --- a/ip/ipmaddr.c +++ b/ip/ipmaddr.c @@ -136,17 +136,18 @@ static void read_igmp(struct ma_info **result_p) while (fgets(buf, sizeof(buf), fp)) { struct ma_info *ma; - size_t len = 0; if (buf[0] != '\t') { + size_t len; + sscanf(buf, "%d%s", &m.index, m.name); len = strlen(m.name); if (m.name[len - 1] == ':') - len--; + m.name[len - 1] = '\0'; continue; } - if (filter.dev && strncmp(filter.dev, m.name, len)) + if (filter.dev && strcmp(filter.dev, m.name)) continue; sscanf(buf, "%08x%d", (__u32 *)&m.addr.data, &m.users); -- 2.47.2