From 3b6ef6334febb05d3050a96546e635f038dbcb15 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Fri, 4 Nov 2011 11:01:46 +0100 Subject: [PATCH] cfg80211: fix cmp_ies When comparing two items by IE, the sort order wasn't stable, which could lead to issues in the rbtree. Make it stable by making a missing IE sort before a present IE. Also sort by length first if it differs and then by contents. Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- net/wireless/scan.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/net/wireless/scan.c b/net/wireless/scan.c index 0fb142410404..dc23b31594e0 100644 --- a/net/wireless/scan.c +++ b/net/wireless/scan.c @@ -259,17 +259,20 @@ static int cmp_ies(u8 num, u8 *ies1, size_t len1, u8 *ies2, size_t len2) { const u8 *ie1 = cfg80211_find_ie(num, ies1, len1); const u8 *ie2 = cfg80211_find_ie(num, ies2, len2); - int r; + /* equal if both missing */ if (!ie1 && !ie2) return 0; - if (!ie1 || !ie2) + /* sort missing IE before (left of) present IE */ + if (!ie1) return -1; + if (!ie2) + return 1; - r = memcmp(ie1 + 2, ie2 + 2, min(ie1[1], ie2[1])); - if (r == 0 && ie1[1] != ie2[1]) + /* sort by length first, then by contents */ + if (ie1[1] != ie2[1]) return ie2[1] - ie1[1]; - return r; + return memcmp(ie1 + 2, ie2 + 2, ie1[1]); } static bool is_bss(struct cfg80211_bss *a,