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Message-Id: <20100908023706.9901D401AF@magilla.sf.frob.com>
Date: Tue, 7 Sep 2010 19:37:06 -0700 (PDT)
From: Roland McGrath <roland@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org, oss-security@...ts.openwall.com,
Solar Designer <solar@...nwall.com>,
Kees Cook <kees.cook@...onical.com>, Al Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Neil Horman <nhorman@...driver.com>, linux-fsdevel@...r.kernel.org,
pageexec@...email.hu,
"Brad Spengler <spender@...ecurity.net>
Eugene Teo" <eugene@...hat.com>
Subject: [PATCH 3/3] 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@...hat.com>
---
fs/exec.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 6f2d777..828dd24 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -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;
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