45 lines
1.1 KiB
Diff
45 lines
1.1 KiB
Diff
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From e6735556ed0a5e791ea81a015a90c130a0eea060 Mon Sep 17 00:00:00 2001
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From: Xi Wang <xi@mit.edu>
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Date: Wed, 20 Feb 2013 12:45:45 -0500
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Subject: [PATCH] nice: fix overflow checking in int_add_no_wrap()
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In C, signed integer overflow is undefined behavior. Many compilers
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optimize away checks like `a + b < a'.
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Use safe precondition testing instead.
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Signed-off-by: Xi Wang <xi@mit.edu>
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Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
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---
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libc/sysdeps/linux/common/nice.c | 10 +++++-----
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1 file changed, 5 insertions(+), 5 deletions(-)
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diff --git a/libc/sysdeps/linux/common/nice.c b/libc/sysdeps/linux/common/nice.c
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index 3694db8..ed39946 100644
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--- a/libc/sysdeps/linux/common/nice.c
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+++ b/libc/sysdeps/linux/common/nice.c
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@@ -25,15 +25,15 @@ static __inline__ _syscall1(int, __syscall_nice, int, incr)
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static __inline__ int int_add_no_wrap(int a, int b)
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{
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- int s = a + b;
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-
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if (b < 0) {
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- if (s > a) s = INT_MIN;
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+ if (a < INT_MIN - b)
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+ return INT_MIN;
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} else {
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- if (s < a) s = INT_MAX;
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+ if (a > INT_MAX - b)
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+ return INT_MAX;
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}
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- return s;
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+ return a + b;
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}
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static __inline__ int __syscall_nice(int incr)
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--
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1.7.10.4
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