* [PATCH] string: Fix buffer overrun in newlib/libc/string/strrchr.c (#184)
@ 2021-10-11 16:41 Keith Packard
2021-10-13 20:40 ` Jeff Johnston
0 siblings, 1 reply; 2+ messages in thread
From: Keith Packard @ 2021-10-11 16:41 UTC (permalink / raw)
To: newlib
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A picolibc user found a buffer overrun error in strrchr which should
apply to newlib.
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From 752c684c5bc571b061913a1f64250f916ed5dfe9 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Mon, 11 Oct 2021 09:24:54 -0700
Subject: [PATCH] string: Fix buffer overrun in
picolibc/newlib/libc/string/strrchr.c (#184)
Reported by prodisDown:
In picolibc/newlib/libc/string/strrchr.c
if (i) { while ((s=strchr(s, i))) { last = s; s++; } } else { last = strchr(s, i); }
Value (for example 0xFFFFFF00) in if (i) can pass test and
then be typecasted to char inside strchr(). Then s++ and then
buffer overrun.
It can be fixed by preventive typecast i = (int) (char) i; or
typecasting inside expression if ((char) i).
Fixed by casting to char.
Signed-off-by: Keith Packard <keithp@keithp.com>
---
newlib/libc/string/strrchr.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/newlib/libc/string/strrchr.c b/newlib/libc/string/strrchr.c
index 95662e35e..c4638fede 100644
--- a/newlib/libc/string/strrchr.c
+++ b/newlib/libc/string/strrchr.c
@@ -50,10 +50,11 @@ strrchr (const char *s,
int i)
{
const char *last = NULL;
+ char c = i;
- if (i)
+ if (c)
{
- while ((s=strchr(s, i)))
+ while ((s=strchr(s, c)))
{
last = s;
s++;
@@ -61,8 +62,8 @@ strrchr (const char *s,
}
else
{
- last = strchr(s, i);
+ last = strchr(s, c);
}
-
+
return (char *) last;
}
--
2.33.0
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--
-keith
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] string: Fix buffer overrun in newlib/libc/string/strrchr.c (#184)
2021-10-11 16:41 [PATCH] string: Fix buffer overrun in newlib/libc/string/strrchr.c (#184) Keith Packard
@ 2021-10-13 20:40 ` Jeff Johnston
0 siblings, 0 replies; 2+ messages in thread
From: Jeff Johnston @ 2021-10-13 20:40 UTC (permalink / raw)
To: Keith Packard; +Cc: Newlib
Thanks Keith, patch applied.
-- Jeff J.
On Mon, Oct 11, 2021 at 12:41 PM Keith Packard <keithp@keithp.com> wrote:
>
> A picolibc user found a buffer overrun error in strrchr which should
> apply to newlib.
>
>
> --
> -keith
>
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2021-10-11 16:41 [PATCH] string: Fix buffer overrun in newlib/libc/string/strrchr.c (#184) Keith Packard
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