From c0fe5b9da9f98b83262717c0090817f1fbb3d8a0 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Fri, 22 Jul 2011 00:25:56 -0400 Subject: [PATCH] check for fd exhaustion in forkpty we cannot report failure after forking, so the idea is to ensure prior to fork that fd 0,1,2 exist. this will prevent dup2 from possibly hitting a resource limit and failing in the child process. fcntl rather than dup2 is used prior to forking to avoid race conditions. --- src/misc/forkpty.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/src/misc/forkpty.c b/src/misc/forkpty.c index 0bbf2de2..07f8d01e 100644 --- a/src/misc/forkpty.c +++ b/src/misc/forkpty.c @@ -1,14 +1,25 @@ #include #include #include +#include int forkpty(int *m, char *name, const struct termios *tio, const struct winsize *ws) { - int s; + int s, t, i, istmp[3]={0}; pid_t pid; if (openpty(m, &s, name, tio, ws) < 0) return -1; - pid = fork(); + + /* Ensure before forking that we don't exceed fd limit */ + for (i=0; i<3; i++) { + if (fcntl(i, F_GETFL) < 0) { + t = fcntl(s, F_DUPFD, i); + if (t<0) break; + else if (t!=i) close(t); + else istmp[i] = 1; + } + } + pid = i==3 ? fork() : -1; if (!pid) { close(*m); setsid(); @@ -19,6 +30,8 @@ int forkpty(int *m, char *name, const struct termios *tio, const struct winsize if (s>2) close(s); return 0; } + for (i=0; i<3; i++) + if (istmp[i]) close(i); close(s); if (pid < 0) close(*m); return pid; -- 2.25.1