[PATCH] Fix modification of read-only string

[David Howells]

In cellserv_parse_address(), when parsing an IPv6 address bounded by
"[...]", it searches the const string for the closing ']' and then modifies
the string to end it at the ']' position.  This previously compiled fine
because strchr() got rid of the const, however in Fedora 44 this is now
detected by the compiler.

Fix this by constructing the desired string in a stack buffer.

Signed-off-by: David Howells <dhowells at redhat.com>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2434693
---
 src/lib_cellserv.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/lib_cellserv.c b/src/lib_cellserv.c
index 1419532..1debec0 100644
--- a/src/lib_cellserv.c
+++ b/src/lib_cellserv.c
@@ -66,13 +66,17 @@ static int cellserv_parse_address(const struct kafs_profile *child,
 	}
 
 	if (v[0] == '[') {
-		char *p;
+		char *p, *q;
 
 		v++;
 		p = strchr(v, ']');
 		if (!p || p[1])
 			goto invalid;
-		p[0] = 0;
+
+		q = alloca(p - v + 1);
+		memcpy(q, v, p - v);
+		q[p - v] = 0;
+		v = q;
 	}
 
 	if (inet_pton(AF_INET6, v, &addr->sin6.sin6_addr) == 1) {