Refactor download payload reset and free

This was done to squash a memory leak in the sync database download
code. When we downloaded a database and then reused the payload struct,
we could find ourselves calling get_fullpath() for the signatures and
overwriting non-freed values we had left over from the database
download.

Refactor the payload_free function into a payload_reset function that we
can call that does NOT free the payload itself, so we can reuse payload
structs. This also allows us to move the payload to the stack in some
call paths, relieving us of the need to alloc space.

Signed-off-by: Dan McGee <dan@archlinux.org>

1 files changed, 23 insertions, 19 deletions

diff --git a/lib/libalpm/be_sync.c b/lib/libalpm/be_sync.c
index 53777d92..e9e816c0 100644
--- a/lib/libalpm/be_sync.c
+++ b/lib/libalpm/be_sync.c
@@ -201,24 +201,25 @@ int SYMEXPORT alpm_db_update(int force, alpm_db_t *db)
 
 	for(i = db->servers; i; i = i->next) {
 		const char *server = i->data;
-		struct dload_payload *payload;
+		struct dload_payload payload;
 		size_t len;
 		int sig_ret = 0;
 
-		CALLOC(payload, 1, sizeof(*payload), RET_ERR(handle, ALPM_ERR_MEMORY, -1));
+		memset(&payload, 0, sizeof(struct dload_payload));
 
 		/* set hard upper limit of 25MiB */
-		payload->max_size = 25 * 1024 * 1024;
+		payload.max_size = 25 * 1024 * 1024;
 
-		/* print server + filename into a buffer (leave space for .sig) */
-		len = strlen(server) + strlen(db->treename) + 9;
-		CALLOC(payload->fileurl, len, sizeof(char), RET_ERR(handle, ALPM_ERR_MEMORY, -1));
-		snprintf(payload->fileurl, len, "%s/%s.db", server, db->treename);
-		payload->handle = handle;
-		payload->force = force;
-		payload->unlink_on_fail = 1;
+		/* print server + filename into a buffer */
+		len = strlen(server) + strlen(db->treename) + 5;
+		MALLOC(payload.fileurl, len, RET_ERR(handle, ALPM_ERR_MEMORY, -1));
+		snprintf(payload.fileurl, len, "%s/%s.db", server, db->treename);
+		payload.handle = handle;
+		payload.force = force;
+		payload.unlink_on_fail = 1;
 
-		ret = _alpm_download(payload, syncpath, NULL);
+		ret = _alpm_download(&payload, syncpath, NULL);
+		_alpm_dload_payload_reset(&payload);
 
 		if(ret == 0 && (level & ALPM_SIG_DATABASE)) {
 			/* an existing sig file is no good at this point */
@@ -231,20 +232,23 @@ int SYMEXPORT alpm_db_update(int force, alpm_db_t *db)
 			free(sigpath);
 
 			/* if we downloaded a DB, we want the .sig from the same server */
-			snprintf(payload->fileurl, len, "%s/%s.db.sig", server, db->treename);
-			payload->handle = handle;
-			payload->force = 1;
-			payload->errors_ok = (level & ALPM_SIG_DATABASE_OPTIONAL);
+			/* print server + filename into a buffer (leave space for .sig) */
+			len = strlen(server) + strlen(db->treename) + 9;
+			MALLOC(payload.fileurl, len, RET_ERR(handle, ALPM_ERR_MEMORY, -1));
+			snprintf(payload.fileurl, len, "%s/%s.db.sig", server, db->treename);
+			payload.handle = handle;
+			payload.force = 1;
+			payload.errors_ok = (level & ALPM_SIG_DATABASE_OPTIONAL);
 
 			/* set hard upper limit of 16KiB */
-			payload->max_size = 16 * 1024;
+			payload.max_size = 16 * 1024;
 
-			sig_ret = _alpm_download(payload, syncpath, NULL);
+			sig_ret = _alpm_download(&payload, syncpath, NULL);
 			/* errors_ok suppresses error messages, but not the return code */
-			sig_ret = payload->errors_ok ? 0 : sig_ret;
+			sig_ret = payload.errors_ok ? 0 : sig_ret;
+			_alpm_dload_payload_reset(&payload);
 		}
 
-		_alpm_dload_payload_free(payload);
 		if(ret != -1 && sig_ret != -1) {
 			break;
 		}