From 2165f38d2582e88e8a9dd9416f34eca7a7672e5a Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Mon, 30 Jul 2012 03:08:51 +0200 Subject: iptables-restore: fix parameter parsing (shows up with gcc-4.7) This patch fixes parameter parsing in iptables-restore since time ago. The problem has shown up with gcc-4.7. This version of gcc seem to perform more agressive memory management than previous. Peter Lekensteyn provided the following sample code similar to the one in iptables-restore: int i = 0; for (;;) { char x[5]; x[i] = '0' + i; if (++i == 4) { x[i] = '\0'; /* terminate string with null byte */ printf("%s\n", x); break; } } Many may expect 0123 as output. But GCC 4.7 does not do that when compiling with optimization enabled (-O1 and higher). It instead puts random data in the first bytes of the character array, which becomes: | 0 | 1 | 2 | 3 | 4 | | RANDOM | '3' | '\0' | Since the array is declared inside the scope of loop's body, you can think of it as of a new array being allocated in the automatic storage area for each loop iteration. The correct code should be: char x[5]; for (;;) { x[i] = '0' + i; if (++i == 4) { x[i] = '\0'; /* terminate string with null byte */ printf("%s\n", x); break; } } Signed-off-by: Pablo Neira Ayuso --- iptables/ip6tables-restore.c | 3 +-- iptables/iptables-restore.c | 3 +-- 2 files changed, 2 insertions(+), 4 deletions(-) diff --git a/iptables/ip6tables-restore.c b/iptables/ip6tables-restore.c index 3894d68d..1ec3dd95 100644 --- a/iptables/ip6tables-restore.c +++ b/iptables/ip6tables-restore.c @@ -329,6 +329,7 @@ int ip6tables_restore_main(int argc, char *argv[]) char *curchar; int quote_open, escaped; size_t param_len; + char param_buffer[1024]; /* reset the newargv */ newargc = 0; @@ -379,8 +380,6 @@ int ip6tables_restore_main(int argc, char *argv[]) param_len = 0; for (curchar = parsestart; *curchar; curchar++) { - char param_buffer[1024]; - if (quote_open) { if (escaped) { param_buffer[param_len++] = *curchar; diff --git a/iptables/iptables-restore.c b/iptables/iptables-restore.c index 034f9606..9f51f993 100644 --- a/iptables/iptables-restore.c +++ b/iptables/iptables-restore.c @@ -329,6 +329,7 @@ iptables_restore_main(int argc, char *argv[]) char *curchar; int quote_open, escaped; size_t param_len; + char param_buffer[1024]; /* reset the newargv */ newargc = 0; @@ -379,8 +380,6 @@ iptables_restore_main(int argc, char *argv[]) param_len = 0; for (curchar = parsestart; *curchar; curchar++) { - char param_buffer[1024]; - if (quote_open) { if (escaped) { param_buffer[param_len++] = *curchar; -- cgit v1.2.3