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[S390] uaccess: implement strict user copy checks

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Same as on x86 and sparc, besides the fact that enabling the option
will just emit compile time warnings instead of errors.
Keeps allyesconfig kernels compiling.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2010-02-26 22:37:22 +01:00 committed by Martin Schwidefsky
parent 68c6b85984
commit 1dcec254af
4 changed files with 34 additions and 1 deletions
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13
arch/s390/Kconfig.debug
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@ -6,4 +6,17 @@ config TRACE_IRQFLAGS_SUPPORT
source "lib/Kconfig.debug"
config DEBUG_STRICT_USER_COPY_CHECKS
bool "Strict user copy size checks"
---help---
Enabling this option turns a certain set of sanity checks for user
copy operations into compile time warnings.
The copy_from_user() etc checks are there to help test if there
are sufficient security checks on the length argument of
the copy operation, by having gcc prove that the argument is
within bounds.
If unsure, or if you run an older (pre 4.4) gcc, say N.
endmenu

12
arch/s390/include/asm/uaccess.h
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@ -265,6 +265,12 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
return uaccess.copy_from_user(n, from, to);
}
extern void copy_from_user_overflow(void)
#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
__compiletime_warning("copy_from_user() buffer size is not provably correct")
#endif
;
/**
* copy_from_user: - Copy a block of data from user space.
* @to: Destination address, in kernel space.
@ -284,7 +290,13 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
static inline unsigned long __must_check
copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned int sz = __compiletime_object_size(to);
might_fault();
if (unlikely(sz != -1 && sz < n)) {
copy_from_user_overflow();
return n;
}
if (access_ok(VERIFY_READ, from, n))
n = __copy_from_user(to, from, n);
else

2
arch/s390/lib/Makefile
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@ -2,7 +2,7 @@
# Makefile for s390-specific library files..
#
lib-y += delay.o string.o uaccess_std.o uaccess_pt.o
lib-y += delay.o string.o uaccess_std.o uaccess_pt.o usercopy.o
obj-$(CONFIG_32BIT) += div64.o qrnnd.o ucmpdi2.o
lib-$(CONFIG_64BIT) += uaccess_mvcos.o
lib-$(CONFIG_SMP) += spinlock.o

8
arch/s390/lib/usercopy.c Normal file
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@ -0,0 +1,8 @@
#include <linux/module.h>
#include <linux/bug.h>
void copy_from_user_overflow(void)
{
WARN(1, "Buffer overflow detected!\n");
}
EXPORT_SYMBOL(copy_from_user_overflow);