uclient-fetch: fix overloading of output_file variable

When uclient-fetch is called with multiple URL's, it derives the
first filename from the URL. It then sets the global output_file
variable, causing a use-after-free bug on an attempt to use it as output
file for the next file.

Fix this by avoiding the overwrite entirely by only setting a local
variable

Reported-by: Philip Prindeville <philipp@redfish-solutions.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/uclient-fetch.c b/uclient-fetch.c
index dff144b..2e553a0 100644 (file)
--- a/uclient-fetch.c
+++ b/uclient-fetch.c
@@ -50,7 +50,7 @@ static bool verify = true;
 static bool proxy = true;
 static bool default_certs = false;
 static bool no_output;
-static const char *output_file;
+static const char *opt_output_file;
 static int output_fd = -1;
 static int error_ret;
 static off_t out_offset;
@@ -97,6 +97,7 @@ get_proxy_url(char *url)
 
 static int open_output_file(const char *path, uint64_t resume_offset)
 {
+       const char *output_file = opt_output_file;
        char *filename = NULL;
        int flags;
        int ret;
@@ -367,7 +368,7 @@ static void request_done(struct uclient *cl)
                        return;
        }
 
-       if (output_fd >= 0 && !output_file) {
+       if (output_fd >= 0 && !opt_output_file) {
                close(output_fd);
                output_fd = -1;
        }
@@ -615,7 +616,7 @@ int main(int argc, char **argv)
                        user_agent = optarg;
                        break;
                case 'O':
-                       output_file = optarg;
+                       opt_output_file = optarg;
                        break;
                case 'P':
                        if (chdir(optarg)) {