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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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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