linux-kernel - Re: [PATCH] powerpc: Add __must_check to set_memory

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Message-ID: <8dcc739a-3fd4-434c-995c-1dce33cefe6f@csgroup.eu>
Date: Wed, 6 Nov 2024 10:39:43 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 Naveen N Rao <naveen@...nel.org>, Nicholas Piggin <npiggin@...il.com>,
 Kees Cook <kees@...nel.org>, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] powerpc: Add __must_check to set_memory_...()

Hi Michael,

Le 07/09/2024 à 17:40, Christophe Leroy a écrit :
> After the following powerpc commits, all calls to set_memory_...()
> functions check returned value.
> - Commit 8f17bd2f4196 ("powerpc: Handle error in mark_rodata_ro() and
> mark_initmem_nx()")
> - Commit f7f18e30b468 ("powerpc/kprobes: Handle error returned by
> set_memory_rox()")
> - Commit 009cf11d4aab ("powerpc: Don't ignore errors from
> set_memory_{n}p() in __kernel_map_pages()")
> - Commit 9cbacb834b4a ("powerpc: Don't ignore errors from
> set_memory_{n}p() in __kernel_map_pages()")
> - Commit 78cb0945f714 ("powerpc: Handle error in mark_rodata_ro() and
> mark_initmem_nx()")
> 
> All calls in core parts of the kernel also always check returned value,
> can be looked at with following query:
> 
>    $ git grep -w -e set_memory_ro -e set_memory_rw -e set_memory_x -e set_memory_nx -e set_memory_rox `find . -maxdepth 1 -type d | grep -v arch | grep /`
> 
> It is now possible to flag those functions with __must_check to make
> sure no new unchecked call it added.
> 
> Link: https://github.com/KSPP/linux/issues/7
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>

Do you plan to take this patch anytime soon ?

The generic part of the same was already applied in previous cycle, see 
https://github.com/torvalds/linux/commit/82ce8e2f31a1eb05b1527c3d807bea40031df913

Discussion at 
https://lore.kernel.org/all/b0fe75b4-c1bb-47f7-a7c3-2534b31c1780@csgroup.eu/T/ 
suggests that it would be beneficial to enforce return checking.

Christophe


> ---
>   arch/powerpc/include/asm/set_memory.h | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
> index 9a025b776a4b..9c8d5747755d 100644
> --- a/arch/powerpc/include/asm/set_memory.h
> +++ b/arch/powerpc/include/asm/set_memory.h
> @@ -12,37 +12,37 @@
>   
>   int change_memory_attr(unsigned long addr, int numpages, long action);
>   
> -static inline int set_memory_ro(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_ro(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_RO);
>   }
>   
> -static inline int set_memory_rw(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_rw(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_RW);
>   }
>   
> -static inline int set_memory_nx(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_nx(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_NX);
>   }
>   
> -static inline int set_memory_x(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_x(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_X);
>   }
>   
> -static inline int set_memory_np(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_np(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_NP);
>   }
>   
> -static inline int set_memory_p(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_p(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_P);
>   }
>   
> -static inline int set_memory_rox(unsigned long addr, int numpages)
> +static inline int __must_check set_memory_rox(unsigned long addr, int numpages)
>   {
>   	return change_memory_attr(addr, numpages, SET_MEMORY_ROX);
>   }