From 6d92d4f6a74766cc885b18218268e0c47fbca399 Mon Sep 17 00:00:00 2001 From: Xi Wang Date: Fri, 11 Jan 2013 14:31:48 -0800 Subject: fs/exec.c: work around icc miscompilation The tricky problem is this check: if (i++ >= max) icc (mis)optimizes this check as: if (++i > max) The check now becomes a no-op since max is MAX_ARG_STRINGS (0x7FFFFFFF). This is "allowed" by the C standard, assuming i++ never overflows, because signed integer overflow is undefined behavior. This optimization effectively reverts the previous commit 362e6663ef23 ("exec.c, compat.c: fix count(), compat_count() bounds checking") that tries to fix the check. This patch simply moves ++ after the check. Signed-off-by: Xi Wang Cc: Jason Baron Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/exec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/exec.c b/fs/exec.c index 18c45cac368..20df02c1cc7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -434,8 +434,9 @@ static int count(struct user_arg_ptr argv, int max) if (IS_ERR(p)) return -EFAULT; - if (i++ >= max) + if (i >= max) return -E2BIG; + ++i; if (fatal_signal_pending(current)) return -ERESTARTNOHAND; -- cgit v1.2.3