diff options
| author | Paul Burton | 2019-02-09 19:47:36 +0000 |
|---|---|---|
| committer | Thomas Bogendoerfer | 2021-04-13 14:28:19 +0200 |
| commit | 168b84d5d2c07ae6c96ea40a7f420b5b525defa0 (patch) | |
| tree | 23ad853364ae834431aa88c347b21944a3be4b6b /arch/mips | |
| parent | dbd815c0dccadffbee5c9780308858fd07669ce2 (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.h | 4 |
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) \ |