[lxc-devel] [PATCH 1/6] fix integer overflow in setproctitle

[Tycho Andersen]

1. prctl() only accepts longs, so we can just scan the stat file as longs.
2. check overflow before addition

Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
---
 src/lxc/utils.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index 1df6e8f..cc12ecd 100644
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -1599,7 +1599,7 @@ int setproctitle(char *title)
 	char buf[2048], *tmp;
 	FILE *f;
 	int i, len, ret = 0;
-	unsigned long arg_start, arg_end, env_start, env_end;
+	long arg_start, arg_end, env_start, env_end;
 
 	f = fopen_cloexec("/proc/self/stat", "r");
 	if (!f) {
@@ -1624,7 +1624,7 @@ int setproctitle(char *title)
 	if (!tmp)
 		return -1;
 
-	i = sscanf(tmp, "%lu %lu %lu %lu", &arg_start, &arg_end, &env_start, &env_end);
+	i = sscanf(tmp, "%ld %ld %ld %ld", &arg_start, &arg_end, &env_start, &env_end);
 	if (i != 4) {
 		return -1;
 	}
@@ -1644,15 +1644,21 @@ int setproctitle(char *title)
 		if (len >= arg_end - arg_start) {
 			env_start = env_end;
 		}
+
+		/* check overflow */
+		if (arg_start + len < 0) {
+			return -1;
+		}
+
 		arg_end = arg_start + len;
 	}
 
 	strcpy((char*)arg_start, title);
 
-	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_START,   (long)arg_start, 0, 0);
-	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_END,     (long)arg_end, 0, 0);
-	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_START,   (long)env_start, 0, 0);
-	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_END,     (long)env_end, 0, 0);
+	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_START,   arg_start, 0, 0);
+	ret |= prctl(PR_SET_MM, PR_SET_MM_ARG_END,     arg_end, 0, 0);
+	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_START,   env_start, 0, 0);
+	ret |= prctl(PR_SET_MM, PR_SET_MM_ENV_END,     env_end, 0, 0);
 
 	return ret;
 }
-- 
2.1.4