[iproute,40/51] tc/m_xt: Fix for potential string buffer overflows

Submitted by Phil Sutter on Aug. 12, 2017, 12:04 p.m.

Details

Message ID 20170812120510.28750-41-phil@nwl.cc
State Changes Requested
Delegated to: stephen hemminger
Headers show

Commit Message

Phil Sutter Aug. 12, 2017, 12:04 p.m.
- Use strncpy() when writing to target->t->u.user.name and make sure the
  final byte remains untouched (xtables_calloc() set it to zero).
- 'tname' length sanitization was completely wrong: If it's length
  exceeded the 16 bytes available in 'k', passing a length value of 16
  to strncpy() would overwrite the previously NULL'ed 'k[15]'. Also, the
  sanitization has to happen if 'tname' is exactly 16 bytes long as
  well.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 tc/m_xt.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

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diff --git a/tc/m_xt.c b/tc/m_xt.c
index ad52d239caf61..9218b14594403 100644
--- a/tc/m_xt.c
+++ b/tc/m_xt.c
@@ -95,7 +95,8 @@  build_st(struct xtables_target *target, struct xt_entry_target *t)
 	if (t == NULL) {
 		target->t = xtables_calloc(1, size);
 		target->t->u.target_size = size;
-		strcpy(target->t->u.user.name, target->name);
+		strncpy(target->t->u.user.name, target->name,
+			sizeof(target->t->u.user.name) - 1);
 		target->t->u.user.revision = target->revision;
 
 		if (target->init != NULL)
@@ -277,8 +278,8 @@  static int parse_ipt(struct action_util *a, int *argc_p,
 	}
 	fprintf(stdout, " index %d\n", index);
 
-	if (strlen(tname) > 16) {
-		size = 16;
+	if (strlen(tname) >= 16) {
+		size = 15;
 		k[15] = 0;
 	} else {
 		size = 1 + strlen(tname);