> On Sun, 18 Jan 2009 12:18:31 +0100 Heiko Carstens <heiko.carstens@xxxxxxxxxx> wrote: > Hi Andrew, > > while debugging I noticed the following comment in fs/binfmt_elf.c: > > /* > * The early SET_PERSONALITY here is so that the lookup > * for the interpreter happens in the namespace of the > * to-be-execed image. SET_PERSONALITY can select an > * alternate root. > * > * However, SET_PERSONALITY is NOT allowed to switch > * this task into the new images's memory mapping > * policy - that is, TASK_SIZE must still evaluate to > * that which is appropriate to the execing application. > * This is because exit_mmap() needs to have TASK_SIZE > * evaluate to the size of the old image. > * > * So if (say) a 64-bit application is execing a 32-bit > * application it is the architecture's responsibility > * to defer changing the value of TASK_SIZE until the > * switch really is going to happen - do this in > * flush_thread(). - akpm > */ Cripes, that must have been a different akpm. > At least s390 isn't doing the deferred TASK_SIZE switch. Also it seems like > MIPS, PARISC and IA64 don't do it either. However from a quick a view I > couldn't see that exit_mmap depends on TASK_SIZE. So is this still necessary? > > And the bug I was looking for is this one: in SET_PERSONALITY we do this: > > if (current->personality != PER_LINUX32) > set_personality(PER_LINUX); > > However we should use the PER_MASK if we want to check for PER_LINUX32, > since there are more bits in the personality flags. In case any of the > 'extra' bits is set we may incorrectly set personality to PER_LINUX even > when we want PER_LINUX32. > > Looks like more architectures should do something like: > > if (personality(current->personality) != PER_LINUX32) > ... I'm stuck in planes and hotels for the rest of the week and don't have a git tree to dig through, sorry. I'd prefer to hold off until next week before diving into that one. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
