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When not logging I/O, use a signal handler that only forwards SIGINT,

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SIGQUIT and SIGHUP when they are user-generated signals.  Fixes a
race in the non-I/O logging path where the command may receive two
keyboard-generated signals; one from the kernel and one from the
sudo process.
This commit is contained in:
Todd C. Miller
2012-01-17 10:27:33 -05:00
parent 97cecaf6eb
commit 2fd77381a1
1 changed files with 44 additions and 3 deletions
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47
src/exec.c
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@@ -78,6 +78,9 @@ static int handle_signals(int fd, pid_t child, int log_io,
struct command_status *cstat);
static void forward_signals(int fd);
static void schedule_signal(int signo);
#ifdef SA_SIGINFO
static void handler_nofwd(int s, siginfo_t *info, void *context);
#endif
/*
* Like execve(2) but falls back to running through /bin/sh
@@ -286,14 +289,28 @@ sudo_execve(struct command_details *details, struct command_status *cstat)
sa.sa_handler = handler;
sigaction(SIGALRM, &sa, NULL);
sigaction(SIGCHLD, &sa, NULL);
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGPIPE, &sa, NULL);
sigaction(SIGQUIT, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
sigaction(SIGUSR1, &sa, NULL);
sigaction(SIGUSR2, &sa, NULL);
/*
* When not running the command in a pty, we do not want to
* forward signals generated by the kernel that the child will
* already have received either by virtue of being in the
* controlling tty's process group (SIGINT, SIGQUIT) or because
* the session is terminating (SIGHUP).
*/
#ifdef SA_SIGINFO
if (!log_io) {
sa.sa_flags |= SA_SIGINFO;
sa.sa_sigaction = handler_nofwd;
}
#endif
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGQUIT, &sa, NULL);
/* Max fd we will be selecting on. */
maxfd = MAX(sv[0], signal_pipe[0]);
@@ -617,6 +634,30 @@ handler(int s)
/* shut up glibc */;
}
#ifdef SA_SIGINFO
/*
* Generic handler for signals passed from parent -> child.
* The other end of signal_pipe is checked in the main event loop.
* This version is for the non-pty case and does not forward
* signals that are generated by the kernel.
*/
static void
handler_nofwd(int s, siginfo_t *info, void *context)
{
unsigned char signo = (unsigned char)s;
/* Only forward user-generated signals. */
if (info->si_code <= 0) {
/*
* The pipe is non-blocking, if we overflow the kernel's pipe
* buffer we drop the signal. This is not a problem in practice.
*/
if (write(signal_pipe[1], &signo, sizeof(signo)) == -1)
/* shut up glibc */;
}
}
#endif /* SA_SIGINFO */
/*
* Open a pipe and make both ends non-blocking.
* Returns 0 on success and -1 on error.