linux-kernel - Re: [PATCH v9 01/26] mm: helper `is_shadow_stack

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <6543c6b6-da86-4c10-9b8c-e5fe6f6f7da9@suse.cz>
Date: Fri, 7 Feb 2025 10:27:10 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Deepak Gupta <debug@...osinc.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>,
 Christian Brauner <brauner@...nel.org>, Peter Zijlstra
 <peterz@...radead.org>, Oleg Nesterov <oleg@...hat.com>,
 Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
 Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
 Jann Horn <jannh@...gle.com>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-arch@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
 alistair.francis@....com, richard.henderson@...aro.org, jim.shu@...ive.com,
 andybnac@...il.com, kito.cheng@...ive.com, charlie@...osinc.com,
 atishp@...osinc.com, evan@...osinc.com, cleger@...osinc.com,
 alexghiti@...osinc.com, samitolvanen@...gle.com, broonie@...nel.org,
 rick.p.edgecombe@...el.com
Subject: Re: [PATCH v9 01/26] mm: helper `is_shadow_stack_vma` to check shadow
 stack vma

On 2/5/25 02:21, Deepak Gupta wrote:
> VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack

I see that arm GCS uses VM_HIGH_ARCH_6.

> VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow

And RISC-V doesn't define it at all, not even in this patchset, or did I
miss it somewhere?

> stack). In case architecture doesn't implement shadow stack, it's VM_NONE
> Introducing a helper `is_shadow_stack_vma` to determine shadow stack vma
> or not.

This looks like an unfinished sentence. As if it was to continue with "...
will allow us to ..." what?

I'm not against a helper but this changelog is rather confusing and also
code in arch/x86 and arch/arm64 isn't converted to the helper but testing
VM_SHADOW_STACK still.

> Signed-off-by: Deepak Gupta <debug@...osinc.com>
> Reviewed-by: Mark Brown <broonie@...nel.org>
> ---
>  mm/gup.c  |  2 +-
>  mm/mmap.c |  2 +-
>  mm/vma.h  | 10 +++++++---
>  3 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 3883b307780e..8c64f3ff34ab 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1291,7 +1291,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
>  		    !writable_file_mapping_allowed(vma, gup_flags))
>  			return -EFAULT;
>  
> -		if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) {
> +		if (!(vm_flags & VM_WRITE) || is_shadow_stack_vma(vm_flags)) {
>  			if (!(gup_flags & FOLL_FORCE))
>  				return -EFAULT;
>  			/*
> diff --git a/mm/mmap.c b/mm/mmap.c
> index cda01071c7b1..7b6be4eec35d 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -648,7 +648,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
>   */
>  static inline unsigned long stack_guard_placement(vm_flags_t vm_flags)
>  {
> -	if (vm_flags & VM_SHADOW_STACK)
> +	if (is_shadow_stack_vma(vm_flags))
>  		return PAGE_SIZE;
>  
>  	return 0;
> diff --git a/mm/vma.h b/mm/vma.h
> index a2e8710b8c47..47482a25f5c3 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -278,7 +278,7 @@ static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi,
>  }
>  
>  /*
> - * These three helpers classifies VMAs for virtual memory accounting.
> + * These four helpers classifies VMAs for virtual memory accounting.
>   */
>  
>  /*
> @@ -289,6 +289,11 @@ static inline bool is_exec_mapping(vm_flags_t flags)
>  	return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC;
>  }
>  
> +static inline bool is_shadow_stack_vma(vm_flags_t vm_flags)
> +{
> +	return !!(vm_flags & VM_SHADOW_STACK);
> +}
> +
>  /*
>   * Stack area (including shadow stacks)
>   *
> @@ -297,7 +302,7 @@ static inline bool is_exec_mapping(vm_flags_t flags)
>   */
>  static inline bool is_stack_mapping(vm_flags_t flags)
>  {
> -	return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK);
> +	return ((flags & VM_STACK) == VM_STACK) || is_shadow_stack_vma(flags);
>  }
>  
>  /*
> @@ -308,7 +313,6 @@ static inline bool is_data_mapping(vm_flags_t flags)
>  	return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
>  }
>  
> -
>  static inline void vma_iter_config(struct vma_iterator *vmi,
>  		unsigned long index, unsigned long last)
>  {
>