[PATCH 2/2] ARM: fix personality flag propagation across an exec

[Russell King - ARM Linux]

On Fri, Apr 08, 2011 at 03:50:21PM -0400, Nicolas Pitre wrote:
> However, if we're only setting the address limit flag here, wouldn't it 
> be better to leave the current personality type as is and only set/clear 
> the ADDR_LIMIT_32BIT flag?  Something like:
> 
> 	unsigned int personality = current->personality;
>         if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
>             (eflags & EF_ARM_APCS_26))
>                 personality &= ~ADDR_LIMIT_32BIT;
>         else
>                 personality |= ADDR_LIMIT_32BIT;
>         set_personality(personality);
> 
> Or is the actual personality type not supposed to be inherited?
> 
> I also notice that bad_syscall() is broken if extra flags such as 
> ADDR_NO_RANDOMIZE are added to the current personality (will send a 
> patch for that as well).

Many architectures explicitly set a personality type on exec, so that
seems to be the thing to do.  We want it set to a PER_LINUX flavour
as the ELF executables we run tend to be Linux executables.

Also, the ARM kernel doesn't really support anything but PER_LINUX
ELF executables, so it'd be rather meaningless to set it to anything
else here.

So:

	unsigned int personality = current->personality & ~PER_MASK;

	/*
	 * We only support Linux ELF executables, so always set the
	 * personality to LINUX.
	 */
	personality |= PER_LINUX;

	/* APCS-26 is only valid for OABI executables */
	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
	    (eflags & EF_ARM_APCS_26))
		personality &= ~ADDR_LIMIT_32BIT;
	else
		personality |= ADDR_LIMIT_32BIT;

	set_personality(personality);

is probably what we want.