Re: [PATCH 0/2] mm: make copy_to_kernel_nofault() not fault on user addresses

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 02/09/2024 à 07:31, Omar Sandoval a écrit :
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> 
> From: Omar Sandoval <osandov@fb.com>
> 
> Hi,
> 
> I hit a case where copy_to_kernel_nofault() will fault (lol): if the
> destination address is in userspace and x86 Supervisor Mode Access
> Prevention is enabled. Patch 2 has the details and the fix. Patch 1
> renames a helper function so that its use in patch 2 makes more sense.
> If the rename is too intrusive, I can drop it.

The name of the function is "copy_to_kernel". If the destination is a 
user address, it is not a copy to kernel but a copy to user and you 
already have the function copy_to_user() for that. copy_to_user() 
properly handles SMAP.

Christophe


> 
> Thanks,
> Omar
> 
> Omar Sandoval (2):
>    mm: rename copy_from_kernel_nofault_allowed() to
>      copy_kernel_nofault_allowed()
>    mm: make copy_to_kernel_nofault() not fault on user addresses
> 
>   arch/arm/mm/fault.c         |  2 +-
>   arch/loongarch/mm/maccess.c |  2 +-
>   arch/mips/mm/maccess.c      |  2 +-
>   arch/parisc/lib/memcpy.c    |  2 +-
>   arch/powerpc/mm/maccess.c   |  2 +-
>   arch/um/kernel/maccess.c    |  2 +-
>   arch/x86/mm/maccess.c       |  4 ++--
>   include/linux/uaccess.h     |  2 +-
>   mm/maccess.c                | 10 ++++++----
>   9 files changed, 15 insertions(+), 13 deletions(-)
> 
> --
> 2.46.0
> 
>