[pacman-dev] [PATCH] alpm_run_chroot: always connect parent2child pipe

[Andrew Gregory]

Commit e374e6829cea3512f0b4a4069c5a6168f0f8d8a0 closed stdin before
running scripts/hooks.  This left the exec'd process with no file
descriptor 0.  If the process subsequently opened a file it would be
assigned fd 0, and could potentially be confused for stdin.  Connecting
and immediately closing the parent2child pipe ensures that the child has
an fd 0 and that it is empty.

Signed-off-by: Andrew Gregory <andrew.gregory.8 at gmail.com>
---
See https://bbs.archlinux.org/viewtopic.php?id=209151

Missing fd 0 has also caused bash to start sourcing ~/.basrc (see
https://lists.archlinux.org/pipermail/pacman-dev/2016-February/020870.html) but
that is due to a bug in bash that has been reported and should get fixed.

 lib/libalpm/util.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index 001c042..4a4847d 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -586,7 +586,7 @@ int _alpm_run_chroot(alpm_handle_t *handle, const char *cmd, char *const argv[],
 		goto cleanup;
 	}
 
-	if(stdin_cb && pipe(parent2child_pipefd) == -1) {
+	if(pipe(parent2child_pipefd) == -1) {
 		_alpm_log(handle, ALPM_LOG_ERROR, _("could not create pipe (%s)\n"), strerror(errno));
 		retval = 1;
 		goto cleanup;
@@ -607,11 +607,9 @@ int _alpm_run_chroot(alpm_handle_t *handle, const char *cmd, char *const argv[],
 		close(2);
 		while(dup2(child2parent_pipefd[1], 1) == -1 && errno == EINTR);
 		while(dup2(child2parent_pipefd[1], 2) == -1 && errno == EINTR);
-		if(stdin_cb) {
-			while(dup2(parent2child_pipefd[0], 0) == -1 && errno == EINTR);
-			close(parent2child_pipefd[0]);
-			close(parent2child_pipefd[1]);
-		}
+		while(dup2(parent2child_pipefd[0], 0) == -1 && errno == EINTR);
+		close(parent2child_pipefd[0]);
+		close(parent2child_pipefd[1]);
 		close(child2parent_pipefd[0]);
 		close(child2parent_pipefd[1]);
 		if(cwdfd >= 0) {
@@ -646,15 +644,16 @@ int _alpm_run_chroot(alpm_handle_t *handle, const char *cmd, char *const argv[],
 		child2parent->events = POLLIN;
 		fcntl(child2parent->fd, F_SETFL, O_NONBLOCK);
 		close(child2parent_pipefd[1]);
+		close(parent2child_pipefd[0]);
 
 		if(stdin_cb) {
 			parent2child->fd = parent2child_pipefd[1];
 			parent2child->events = POLLOUT;
 			fcntl(parent2child->fd, F_SETFL, O_NONBLOCK);
-			close(parent2child_pipefd[0]);
 		} else {
 			parent2child->fd = -1;
 			parent2child->events = 0;
+			close(parent2child_pipefd[1]);
 		}
 
 #define STOP_POLLING(p) do { close(p->fd); p->fd = -1; } while(0)
-- 
2.7.1