git: 0899f7a3b791 - main - ifconfig: Fix invalid free() in ifbridge

The branch main has been updated by ivy:

URL: https://cgit.FreeBSD.org/src/commit/?id=0899f7a3b791ed4878e7cb3859636ec980c76832

commit 0899f7a3b791ed4878e7cb3859636ec980c76832
Author:     Lexi Winter <ivy@FreeBSD.org>
AuthorDate: 2025-11-04 00:53:25 +0000
Commit:     Lexi Winter <ivy@FreeBSD.org>
CommitDate: 2025-11-04 00:53:25 +0000

    ifconfig: Fix invalid free() in ifbridge
    
    parse_vlans() does 's = strdup(str)', then calls strsep(&s, ...), then
    attempts to free(s) at the end of the function.  For the success case,
    this is fine (s is NULL, so it's a trivial memory leak), but in the
    error case, we will attempt to free an invalid pointer.
    
    Fix this by storing the original return value from strdup() and freeing
    that instead.
    
    MFC after:      3 seconds
    Reported by:    David Gwynne <dlg@openbsd.org>
    Reviewed by:    zlei, kevans
    Sponsored by:   https://www.patreon.com/bsdivy
    Differential Revision:  https://reviews.freebsd.org/D53545
---
 sbin/ifconfig/ifbridge.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sbin/ifconfig/ifbridge.c b/sbin/ifconfig/ifbridge.c
index eff443447c13..8bcf4a638adf 100644
--- a/sbin/ifconfig/ifbridge.c
+++ b/sbin/ifconfig/ifbridge.c
@@ -811,7 +811,7 @@ unsetbridge_private(if_ctx *ctx, const char *val, int dummy __unused)
 static int
 parse_vlans(ifbvlan_set_t *set, const char *str)
 {
-	char *s, *token;
+	char *s, *free_s, *token;
 
 	/* "none" means the empty vlan set */
 	if (strcmp(str, "none") == 0) {
@@ -829,6 +829,8 @@ parse_vlans(ifbvlan_set_t *set, const char *str)
 
 	if ((s = strdup(str)) == NULL)
 		return (-1);
+	/* Keep the original value of s, since strsep() will modify it */
+	free_s = s;
 
 	while ((token = strsep(&s, ",")) != NULL) {
 		unsigned long first, last;
@@ -856,11 +858,11 @@ parse_vlans(ifbvlan_set_t *set, const char *str)
 			BRVLAN_SET(set, vlan);
 	}
 
-	free(s);
+	free(free_s);
 	return (0);
 
 err:
-	free(s);
+	free(free_s);
 	return (-1);
 }