Mirrors/libwebsockets
1
0
Fork 0
mirror of https://github.com/warmcat/libwebsockets.git synced 2025-03-09 00:00:04 +01:00
Code Issues Releases Wiki Activity

vfork

Browse source 
There's a subtle difference between fork and vfork... when doing the
dup() before the exec, with cfork we are still dealing with the
parent process "possessed" by the forked process briefly inbetween
the vfork() and the exec().

That matters because when we close the duplicated fds for the stdxxx
pipes, with vfork we're closing the fd we still want to hold in the
parent process.
This commit is contained in:
Andy Green 2020-04-01 05:56:45 +01:00
parent 39b05e7db3
commit 4caeb56bec
1 changed files with 13 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
lib/misc/spawn.c
View file

@ -362,7 +362,7 @@ lws_spawn_piped(const struct lws_spawn_piped_info *i)
if (lws_change_pollfd(lsp->stdwsi[LWS_STDERR], LWS_POLLOUT, LWS_POLLIN))
goto bail3;
lwsl_debug("%s: fds in %d, out %d, err %d\n", __func__,
lwsl_notice("%s: fds in %d, out %d, err %d\n", __func__,
lsp->stdwsi[LWS_STDIN]->desc.sockfd,
lsp->stdwsi[LWS_STDOUT]->desc.sockfd,
lsp->stdwsi[LWS_STDERR]->desc.sockfd);
@ -448,8 +448,18 @@ lws_spawn_piped(const struct lws_spawn_piped_info *i)
lwsl_err("%s: stdin dup2 failed\n", __func__);
goto bail3;
}
close(lsp->pipe_fds[m][0]);
close(lsp->pipe_fds[m][1]);
/*
* If we used fork(), then we can close both sides of the
* original pipe now we bound it to fd 0, 1, 2.
*
* But if we used vfork(), until the exec() we have hijacked
* the original process temporarily and we are (ab)using its
* identity during this pre-exec() time
*/
close(lsp->pipe_fds[m][!(m == 0)]);
#if !defined(LWS_HAVE_VFORK) || !defined(LWS_HAVE_EXECVPE)
close(lsp->pipe_fds[m][!!(m == 0)]);
#endif
}
// lwsl_notice("%s: child cd %s, exec %s\n", __func__, wd, i->exec_array[0]);