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use sockets for scriptlet/hook communication

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If a scriptlet/hook dies at the wrong moment it can trigger SIGPIPE,
terminating the process.  For pipes, there is no way to prevent SIGPIPE
other than ignoring it process-wide.  This can have unintended
consequences in a multi-threaded process.  Using send(2) with sockets,
however, allows ignoring SIGPIPE on a per-call basis, leaving other
threads able to make use of SIGPIPE.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
This commit is contained in:
Andrew Gregory 2017-04-15 18:22:51 -04:00
parent 6d1dcf7937
commit 6a4c6a02de
1 changed files with 4 additions and 13 deletions
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17
lib/libalpm/util.c
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@ -30,6 +30,7 @@
#include <errno.h>
#include <limits.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <fnmatch.h>
#include <poll.h>
@ -463,7 +464,6 @@ static int _alpm_chroot_write_to_child(alpm_handle_t *handle, int fd,
_alpm_cb_io out_cb, void *cb_ctx)
{
ssize_t nwrite;
struct sigaction newaction, oldaction;
if(*buf_size == 0) {
/* empty buffer, ask the callback for more */
@ -473,16 +473,7 @@ static int _alpm_chroot_write_to_child(alpm_handle_t *handle, int fd,
}
}
/* ignore SIGPIPE in case the pipe has been closed */
newaction.sa_handler = SIG_IGN;
sigemptyset(&newaction.sa_mask);
newaction.sa_flags = 0;
sigaction(SIGPIPE, &newaction, &oldaction);
nwrite = write(fd, buf, *buf_size);
/* restore previous SIGPIPE handler */
sigaction(SIGPIPE, &oldaction, NULL);
nwrite = send(fd, buf, *buf_size, MSG_NOSIGNAL);
if(nwrite != -1) {
/* write was successful, remove the written data from the buffer */
@ -592,13 +583,13 @@ int _alpm_run_chroot(alpm_handle_t *handle, const char *cmd, char *const argv[],
/* Flush open fds before fork() to avoid cloning buffers */
fflush(NULL);
if(pipe(child2parent_pipefd) == -1) {
if(socketpair(AF_UNIX, SOCK_STREAM, 0, child2parent_pipefd) == -1) {
_alpm_log(handle, ALPM_LOG_ERROR, _("could not create pipe (%s)\n"), strerror(errno));
retval = 1;
goto cleanup;
}
if(pipe(parent2child_pipefd) == -1) {
if(socketpair(AF_UNIX, SOCK_STREAM, 0, parent2child_pipefd) == -1) {
_alpm_log(handle, ALPM_LOG_ERROR, _("could not create pipe (%s)\n"), strerror(errno));
retval = 1;
goto cleanup;