Gobinda Charan Maji <gobinda.cemk07@xxxxxxxxx> writes:
> There were some inconsistency in restriction to VERIFY_OCTAL_PERMISSIONS().
> Previously the test was "User perms >= group perms >= other perms". The
> permission field of User, Group or Other consists of three bits. LSB is
> EXECUTE permission, MSB is READ permission and the middle bit is WRITE
> permission. But logically WRITE is "more privileged" than READ.
>
> Say for example, permission value is "0430". Here User has only READ
> permission whereas Group has both WRITE and EXECUTE permission.
>
> So, the checks could be tightened and the tests are separated to
> USER_READABLE >= GROUP_READABLE >= OTHER_READABLE,
> USER_WRITABLE >= GROUP_WRITABLE and OTHER_WRITABLE is not permitted.
>
> Signed-off-by: Gobinda Charan Maji <gobinda.cemk07@xxxxxxxxx>
Thanks, applied!
Cheers,
Rusty.
> ---
> include/linux/kernel.h | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 3a5b48e..cd54b35 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -818,13 +818,15 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
> #endif
>
> /* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
> -#define VERIFY_OCTAL_PERMISSIONS(perms) \
> - (BUILD_BUG_ON_ZERO((perms) < 0) + \
> - BUILD_BUG_ON_ZERO((perms) > 0777) + \
> - /* User perms >= group perms >= other perms */ \
> - BUILD_BUG_ON_ZERO(((perms) >> 6) < (((perms) >> 3) & 7)) + \
> - BUILD_BUG_ON_ZERO((((perms) >> 3) & 7) < ((perms) & 7)) + \
> - /* Other writable? Generally considered a bad idea. */ \
> - BUILD_BUG_ON_ZERO((perms) & 2) + \
> +#define VERIFY_OCTAL_PERMISSIONS(perms) \
> + (BUILD_BUG_ON_ZERO((perms) < 0) + \
> + BUILD_BUG_ON_ZERO((perms) > 0777) + \
> + /* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */ \
> + BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) + \
> + BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) + \
> + /* USER_WRITABLE >= GROUP_WRITABLE */ \
> + BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) + \
> + /* OTHER_WRITABLE? Generally considered a bad idea. */ \
> + BUILD_BUG_ON_ZERO((perms) & 2) + \
> (perms))
> #endif
> --
> 1.8.1.4
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