Re: [v4] Fix to avoid IS_ERR_VALUE and IS_ERR abuses on 64bit systems.
From: Arnd Bergmann <arnd@arndb.de>
Date: 2016-08-01 07:04:32
Also in:
linux-wireless, netdev
On Sunday, July 31, 2016 4:48:44 PM CEST Arvind Yadav wrote:
IS_ERR_VALUE() assumes that parameter is an unsigned long. It can not be used to check if 'unsigned int' is passed insted. Which tends to reflect an error. In 64bit architectures sizeof (int) == 4 && sizeof (long) == 8. IS_ERR_VALUE(x) is ((x) >= (unsigned long)-4095). IS_ERR_VALUE() of 'unsigned int' is always false because the 32bit value is zero extended to 64 bits. Value of (unsigned int)-4095 is always less than value of (unsigned long)-4095. Now We are taking only first 32 bit for error checking rest of the 32 bit we ignore such that we get appropriate comparison on 64bit system as well.
This is completely wrong: if you have a valid 64-bit pointer like 0x00001234ffffff00, this will be interpreted as an error now.
quoted hunk ↗ jump to hunk
First 32bit of Value of (unsigned int)-4095 and (unsigned long)-4095 will be equal. Signed-off-by: Arvind Yadav <redacted> --- include/linux/err.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)diff --git a/include/linux/err.h b/include/linux/err.h index 1e35588..c2a2789 100644 --- a/include/linux/err.h +++ b/include/linux/err.h@@ -18,7 +18,17 @@ #ifndef __ASSEMBLY__ -#define IS_ERR_VALUE(x) unlikely((unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO) +#define IS_ERR_VALUE(x) unlikely(is_error_check(x)) + +static inline int is_error_check(unsigned long error)
Please leave the existing macro alone. I think you were looking for something specific to the return code of qe_muram_alloc() function, so please add a helper in that subsystem if you need it, not in the generic header files. Arnd