Arnd Bergmann wrote:
>
> I have been looking for more places in 2.5 that can be marked
> might_sleep() and noticed that all the functions in asm/uaccess.h
> are not marked although they sleep if the memory they access
> has to be paged in.
>
> After adding might_sleep() in ten places in asm-i386/uaccess.h
> and arch/i386/lib/usercopy.c, I have been running this kernel
> for about two weeks.
This is an excellent point. If someone is holding a lock
across a uaccess function and userspace has passed the address
of a valid but not-present page we will hit the "atomic copy_user"
path. Userspace will be returned an EFAULT and will be left
scratching its head, wondering what it did wrong.
Or the kernel will deadlock, of course.
I don't think we need to add the check to anything other than
ia32. That will pick up the great bulk of any problems, and
arch-specific code won't be doing these copies much anyway.
So if you could prepare a patch which adds these checks for
ia32 it would be muchly appreciated.
And if you're feeling really keen, Dave Jones has a patch which
makes the might_sleep check a real config option rather than
overloading CONFIG_DEBUG_KERNEL - would be nice to squeeze that
out of him if poss.
Thanks.
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This archive was generated by hypermail 2b29 : Thu Nov 07 2002 - 22:00:20 EST