From 519af5ad34fa19fb48e2bc6539135fe0852210c3 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 2 Jul 2013 11:31:24 +0200 Subject: Replace suspicious popen_pid assignment with an obviously correct one popen_pid = vfork() does work correctly, but for a subtle reason that wrong assignment of 0 happens in the child _first_, and _then_ correct value overwrites it in the parent. (And in a hyphothetical system where vfork = fork, popen_pid wouldn't be shared, so it will also be ok.) However, it's not necessary to be difficult. This change makes it so that assignment is done only in parent. Signed-off-by: Denys Vlasenko --- strace.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/strace.c b/strace.c index 4c70b98..2741201 100644 --- a/strace.c +++ b/strace.c @@ -485,6 +485,7 @@ static FILE * strace_popen(const char *command) { FILE *fp; + int pid; int fds[2]; swap_uid(); @@ -493,11 +494,11 @@ strace_popen(const char *command) set_cloexec_flag(fds[1]); /* never fails */ - popen_pid = vfork(); - if (popen_pid == -1) + pid = vfork(); + if (pid < 0) perror_msg_and_die("vfork"); - if (popen_pid == 0) { + if (pid == 0) { /* child */ close(fds[1]); if (fds[0] != 0) { @@ -510,6 +511,7 @@ strace_popen(const char *command) } /* parent */ + popen_pid = pid; close(fds[0]); swap_uid(); fp = fdopen(fds[1], "w"); -- cgit v1.2.3