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authorPaul Burton2019-02-09 19:47:36 +0000
committerThomas Bogendoerfer2021-04-13 14:28:19 +0200
commit168b84d5d2c07ae6c96ea40a7f420b5b525defa0 (patch)
tree23ad853364ae834431aa88c347b21944a3be4b6b /arch/mips
parentdbd815c0dccadffbee5c9780308858fd07669ce2 (diff)
MIPS: Fix access_ok() for the last byte of user space
The MIPS implementation of access_ok() incorrectly reports that access to the final byte of user memory is not OK, much as the alpha & SH versions did prior to commit 94bd8a05cd4d ("Fix 'acccess_ok()' on alpha and SH"). For example on a MIPS64 system with __UA_LIMIT == 0xffff000000000000 we incorrectly fail in the following cases: access_ok(0xffffffffffff, 0x1) = 0 access_ok(0xfffffffffffe, 0x2) = 0 Fix MIPS in the same way as alpha & SH, by subtracting one from the addr + size condition when size is non-zero. With this the access_ok() calls above return 1 indicating that the access may be valid. The cost of the improved check is pretty minimal - we gain 2410 bytes, or 0.03%, in kernel code size for a 64r6el_defconfig kernel built using GCC 8.1.0. Signed-off-by: Paul Burton <paul.burton@mips.com> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Diffstat (limited to 'arch/mips')
-rw-r--r--arch/mips/include/asm/uaccess.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index 9e9e3aa9c341..ab47e597656a 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -79,7 +79,9 @@ extern u64 __ua_limit;
static inline int __access_ok(const void __user *p, unsigned long size)
{
unsigned long addr = (unsigned long)p;
- return (__UA_LIMIT & (addr | (addr + size) | __ua_size(size))) == 0;
+ unsigned long end = addr + size - !!size;
+
+ return (__UA_LIMIT & (addr | end | __ua_size(size))) == 0;
}
#define access_ok(addr, size) \