sandbox: do not resolve target of stderr

The recent e12fee192ac8b0343a468e5a8f7811a7b029ff9a commit does not
handle things when stderr is connected to a real file (e.g. a pipe
or a socket or fifo or ...).  It also does not play well to have
multiple things writing to the same file through different fds.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/src/sandbox.c b/src/sandbox.c
index 51f2d95..3783bca 100644
--- a/src/sandbox.c
+++ b/src/sandbox.c
@@ -82,15 +82,18 @@ static int setup_sandbox(struct sandbox_info_t *sandbox_info, bool interactive)
 	}
 
 	/* Generate sandbox message path -- this process's stderr */
-	char path[SB_PATH_MAX];
-	sprintf(path, "%s/2", sb_get_fd_dir());
-	if (realpath(path, sandbox_info->sandbox_message_path) == NULL) {
-		sb_pwarn("could not read stderr path: %s", path);
+	const char *fdpath = sb_get_fd_dir();
+	if (realpath(fdpath, sandbox_info->sandbox_message_path) == NULL) {
+		sb_pwarn("could not read fd path: %s", fdpath);
 		if (realpath(sbio_fallback_path, sandbox_info->sandbox_message_path)) {
 			sb_pwarn("could not read stderr path: %s", sbio_fallback_path);
 			/* fuck it */
 			strcpy(sandbox_info->sandbox_message_path, sbio_fallback_path);
 		}
+	} else {
+		/* Do not resolve the target of stderr because it could be something
+		 * that doesn't exist on the fs.  Like a pipe (`tee` and such). */
+		strcat(sandbox_info->sandbox_message_path, "/2");
 	}
 
 	return 0;