[src-draft/trunk]: src/sys/net80211 Avoid using sprintf into an auto-sizing s...

[Martin Husemann <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src-all/rev/bdef6703fd9d
branches:  trunk
changeset: 375195:bdef6703fd9d
user:      Martin Husemann <martin%NetBSD.org@localhost>
date:      Tue Dec 14 21:19:26 2021 +0100

description:
Avoid using sprintf into an auto-sizing sbuf while holding a spin mutex.

diffstat:

 sys/net80211/ieee80211.c |  10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diffs (20 lines):

diff -r 04d3c1be19ea -r bdef6703fd9d sys/net80211/ieee80211.c
--- a/sys/net80211/ieee80211.c  Sun Dec 12 13:32:01 2021 +0100
+++ b/sys/net80211/ieee80211.c  Tue Dec 14 21:19:26 2021 +0100
@@ -369,7 +369,15 @@ sysctl_ieee80211coms(SYSCTLFN_ARGS)
        int error, len, cnt = 0;
 
        RUN_ONCE(&ic_list_mtx_once, ic_list_mtx_init);
-       sb = sbuf_new_auto();
+       mtx_lock(&ic_list_mtx);
+       len = 0;
+       LIST_FOREACH(ic, &ic_head, ic_next) {
+               if (len)
+                       len++;
+               len += strlen(ic->ic_name);
+       }
+       mtx_unlock(&ic_list_mtx);
+       sb = sbuf_new(NULL, NULL, len+20 /* some slope */, 0);
        mtx_lock(&ic_list_mtx);
        LIST_FOREACH(ic, &ic_head, ic_next) {
                sbuf_printf(sb, "%s%s", sp, ic->ic_name);