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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>
This commit is contained in:
Roland McGrath 2010-09-07 19:37:06 -07:00 committed by Linus Torvalds
parent 7993bc1f46
commit 9aea5a65aa
1 changed files with 7 additions and 0 deletions
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7
fs/exec.c
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@ -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;