paxldso: switch from a static sized path buffer to dynamic

We keep the buffer around to avoid the malloc overhead between calls,
and we should really only need to grow it once or twice.  This way we
work with an sized lib path and not just the static limit.

1 files changed, 21 insertions, 3 deletions

diff --git a/paxldso.c b/paxldso.c
index 67f317c..61d7962 100644
--- a/paxldso.c
+++ b/paxldso.c
@@ -17,6 +17,9 @@
 static void *ldcache = NULL;
 static size_t ldcache_size = 0;
 
+static char *ldso_cache_buf = NULL;
+static size_t ldso_cache_buf_size = 0;
+
 /* Defines can be seen in glibc's sysdeps/generic/ldconfig.h */
 #define LDSO_CACHE_MAGIC "ld.so-"
 #define LDSO_CACHE_MAGIC_LEN (sizeof LDSO_CACHE_MAGIC -1)
@@ -45,8 +48,8 @@ static size_t ldcache_size = 0;
 char *ldso_cache_lookup_lib(elfobj *elf, const char *fname)
 {
 	int fd;
+	char *ret = NULL;
 	char *strs;
-	static char buf[__PAX_UTILS_PATH_MAX] = "";
 	const char *cachefile = root_rel_path("/etc/ld.so.cache");
 	struct stat st;
 
@@ -92,6 +95,9 @@ char *ldso_cache_lookup_lib(elfobj *elf, const char *fname)
 			ldcache = NULL;
 			return NULL;
 		}
+
+		ldso_cache_buf_size = 4096;
+		ldso_cache_buf = xrealloc(ldso_cache_buf, ldso_cache_buf_size);
 	} else
 		header = ldcache;
 
@@ -99,6 +105,9 @@ char *ldso_cache_lookup_lib(elfobj *elf, const char *fname)
 	strs = (char *) &libent[header->nlibs];
 
 	for (fd = 0; fd < header->nlibs; ++fd) {
+		const char *lib;
+		size_t lib_len;
+
 		/* This should be more fine grained, but for now we assume that
 		 * diff arches will not be cached together, and we ignore the
 		 * the different multilib mips cases.
@@ -112,17 +121,26 @@ char *ldso_cache_lookup_lib(elfobj *elf, const char *fname)
 			continue;
 
 		/* Return first hit because that is how the ldso rolls */
-		strncpy(buf, strs + libent[fd].liboffset, sizeof(buf));
+		lib = strs + libent[fd].liboffset;
+		lib_len = strlen(lib) + 1;
+		if (lib_len > ldso_cache_buf_size) {
+			ldso_cache_buf = xrealloc(ldso_cache_buf, ldso_cache_buf_size + 4096);
+			ldso_cache_buf_size += 4096;
+		}
+		memcpy(ldso_cache_buf, lib, lib_len);
+		ret = ldso_cache_buf;
 		break;
 	}
 
-	return buf;
+	return ret;
 }
 
 #endif
 
 static void ldso_cache_cleanup(void)
 {
+	free(ldso_cache_buf);
+
 	if (ldcache != NULL)
 		munmap(ldcache, ldcache_size);
 }