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 362e6663ef
("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 <xi.wang@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
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1 changed files with 2 additions and 1 deletions
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@ -434,8 +434,9 @@ static int count(struct user_arg_ptr argv, int max)
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if (IS_ERR(p))
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return -EFAULT;
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if (i++ >= max)
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if (i >= max)
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return -E2BIG;
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++i;
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if (fatal_signal_pending(current))
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return -ERESTARTNOHAND;
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