Commit 9aea5a65 authored Sep 07, 2010 by Roland McGrath Committed by Linus Torvalds Sep 10, 2010

execve: make responsive to SIGKILL with large arguments

An execve with a very large total of argument/environment strings
can take a really long time in the execve system call. It runs
uninterruptibly to count and copy all the strings. This change
makes it abort the exec quickly if sent a SIGKILL.

Note that this is the conservative change, to interrupt only for
SIGKILL, by using fatal_signal_pending(). It would be perfectly
correct semantics to let any signal interrupt the string-copying in
execve, i.e. use signal_pending() instead of fatal_signal_pending().
We'll save that change for later, since it could have user-visible
consequences, such as having a timer set too quickly make it so that
an execve can never complete, though it always happened to work before.

Signed-off-by: Roland McGrath <roland@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 7993bc1f

fs/exec.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -376,6 +376,9 @@ static int count(const char __user * const __user * argv, int max)
		argv++;
		if (i++ >= max)
		return -E2BIG;

		if (fatal_signal_pending(current))
		return -ERESTARTNOHAND;
		cond_resched();
		}
		}
		@@ -419,6 +422,10 @@ static int copy_strings(int argc, const char __user const __user argv,
		while (len > 0) {
		int offset, bytes_to_copy;

		if (fatal_signal_pending(current)) {
		ret = -ERESTARTNOHAND;
		goto out;
		}
		cond_resched();

		offset = pos % PAGE_SIZE;