[v2] RISC-V: cpu: refactor deprecated strncpy

Commit Message

Justin Stitt Aug. 2, 2023, 12:21 a.m. UTC

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

Favor not copying strings onto stack and instead use strings directly.
This avoids hard-coding sizes and buffer lengths all together.

Link: https://github.com/KSPP/linux/issues/90
Cc: [e-mail]
Suggested-by: Kees Cook <[e-mail]>
Signed-off-by: Justin Stitt <[e-mail]>
---
Changes in v2:
- Use strings directly instead of copying onto stack with `strscpy` (thanks Kees)
- Link to v1: https://lore.kernel.org/r/[e-mail]
---
 arch/riscv/kernel/cpu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)


---
base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
change-id: 20230801-arch-riscv-kernel-14a048cc6467

Best regards,
--
Justin Stitt <[e-mail]>

Comments

Conor Dooley Aug. 2, 2023, 8:22 p.m. UTC | #1

On Wed, Aug 02, 2023 at 12:21:58AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Favor not copying strings onto stack and instead use strings directly.
> This avoids hard-coding sizes and buffer lengths all together.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [e-mail]
> Suggested-by: Kees Cook <[e-mail]>
> Signed-off-by: Justin Stitt <[e-mail]>
> ---
> Changes in v2:
> - Use strings directly instead of copying onto stack with `strscpy` (thanks Kees)

Yeah, that is what I was thinking of when I decried it as being horrid.
Reviewed-by: Conor Dooley <[e-mail]>

Thanks,
Conor.

Kees Cook Aug. 2, 2023, 8:36 p.m. UTC | #2

On Wed, Aug 02, 2023 at 12:21:58AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Favor not copying strings onto stack and instead use strings directly.
> This avoids hard-coding sizes and buffer lengths all together.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [e-mail]
> Suggested-by: Kees Cook <[e-mail]>
> Signed-off-by: Justin Stitt <[e-mail]>

I like it! ;)

Reviewed-by: Kees Cook <[e-mail]>

Palmer Dabbelt Aug. 2, 2023, 8:41 p.m. UTC | #3

On Wed, 02 Aug 2023 13:36:03 PDT (-0700), [e-mail] wrote:
> On Wed, Aug 02, 2023 at 12:21:58AM +0000, Justin Stitt wrote:
>> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>>
>> Favor not copying strings onto stack and instead use strings directly.
>> This avoids hard-coding sizes and buffer lengths all together.
>>
>> Link: https://github.com/KSPP/linux/issues/90
>> Cc: [e-mail]
>> Suggested-by: Kees Cook <[e-mail]>
>> Signed-off-by: Justin Stitt <[e-mail]>
>
> I like it! ;)
>
> Reviewed-by: Kees Cook <[e-mail]>

Thanks, I just queue it up for fixes (might take a bit to build test, 
I'm a bit backed up).

Reviewed-by: Palmer Dabbelt <[e-mail]>
Acked-by: Palmer Dabbelt <[e-mail]>

If you wanted to take it for some hardening thing, though -- otherwise 
it'll likely end up on my fixes later today.

Palmer Dabbelt Aug. 2, 2023, 8:47 p.m. UTC | #4

On Wed, 02 Aug 2023 13:41:52 PDT (-0700), Palmer Dabbelt wrote:
> On Wed, 02 Aug 2023 13:36:03 PDT (-0700), [e-mail] wrote:
>> On Wed, Aug 02, 2023 at 12:21:58AM +0000, Justin Stitt wrote:
>>> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>>>
>>> Favor not copying strings onto stack and instead use strings directly.
>>> This avoids hard-coding sizes and buffer lengths all together.
>>>
>>> Link: https://github.com/KSPP/linux/issues/90
>>> Cc: [e-mail]
>>> Suggested-by: Kees Cook <[e-mail]>
>>> Signed-off-by: Justin Stitt <[e-mail]>
>>
>> I like it! ;)
>>
>> Reviewed-by: Kees Cook <[e-mail]>
>
> Thanks, I just queue it up for fixes (might take a bit to build test,
> I'm a bit backed up).
>
> Reviewed-by: Palmer Dabbelt <[e-mail]>
> Acked-by: Palmer Dabbelt <[e-mail]>
> 
> If you wanted to take it for some hardening thing, though -- otherwise
> it'll likely end up on my fixes later today.

Sorry this is for-next as it's not a fix, I was just looking at other 
fixes.  It's queued up aimed at for-next.

Kees Cook Aug. 2, 2023, 8:59 p.m. UTC | #5

On August 2, 2023 1:47:14 PM PDT, Palmer Dabbelt <[e-mail]> wrote:
>On Wed, 02 Aug 2023 13:41:52 PDT (-0700), Palmer Dabbelt wrote:
>> On Wed, 02 Aug 2023 13:36:03 PDT (-0700), [e-mail] wrote:
>>> On Wed, Aug 02, 2023 at 12:21:58AM +0000, Justin Stitt wrote:
>>>> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
>>>>
>>>> Favor not copying strings onto stack and instead use strings directly.
>>>> This avoids hard-coding sizes and buffer lengths all together.
>>>>
>>>> Link: https://github.com/KSPP/linux/issues/90
>>>> Cc: [e-mail]
>>>> Suggested-by: Kees Cook <[e-mail]>
>>>> Signed-off-by: Justin Stitt <[e-mail]>
>>>
>>> I like it! ;)
>>>
>>> Reviewed-by: Kees Cook <[e-mail]>
>>
>> Thanks, I just queue it up for fixes (might take a bit to build test,
>> I'm a bit backed up).
>>
>> Reviewed-by: Palmer Dabbelt <[e-mail]>
>> Acked-by: Palmer Dabbelt <[e-mail]>
>> 
>> If you wanted to take it for some hardening thing, though -- otherwise
>> it'll likely end up on my fixes later today.
>
>Sorry this is for-next as it's not a fix, I was just looking at other 
>fixes.  It's queued up aimed at for-next.

Awesome; thank you! :)

Palmer Dabbelt Aug. 9, 2023, 2:11 p.m. UTC | #6

On Wed, 02 Aug 2023 00:21:58 +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Favor not copying strings onto stack and instead use strings directly.
> This avoids hard-coding sizes and buffer lengths all together.
> 
> 

Applied, thanks!

[1/1] RISC-V: cpu: refactor deprecated strncpy
      https://git.kernel.org/palmer/c/12d61a1bc28e

Best regards,

[e-mail] Aug. 9, 2023, 2:20 p.m. UTC | #7

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[e-mail]>:

On Wed, 02 Aug 2023 00:21:58 +0000 you wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Favor not copying strings onto stack and instead use strings directly.
> This avoids hard-coding sizes and buffer lengths all together.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [e-mail]
> Suggested-by: Kees Cook <[e-mail]>
> Signed-off-by: Justin Stitt <[e-mail]>
> 
> [...]

Here is the summary with links:
  - [v2] RISC-V: cpu: refactor deprecated strncpy
    https://git.kernel.org/riscv/c/12d61a1bc28e

You are awesome, thank you!

Patch

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index a2fc952318e9..872fa7a47d68 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -271,21 +271,21 @@  static void print_isa(struct seq_file *f, const char *isa)
 
 static void print_mmu(struct seq_file *f)
 {
-	char sv_type[16];
+	const char *sv_type;
 
 #ifdef CONFIG_MMU
 #if defined(CONFIG_32BIT)
-	strncpy(sv_type, "sv32", 5);
+	sv_type = "sv32";
 #elif defined(CONFIG_64BIT)
 	if (pgtable_l5_enabled)
-		strncpy(sv_type, "sv57", 5);
+		sv_type = "sv57";
 	else if (pgtable_l4_enabled)
-		strncpy(sv_type, "sv48", 5);
+		sv_type = "sv48";
 	else
-		strncpy(sv_type, "sv39", 5);
+		sv_type = "sv39";
 #endif
 #else
-	strncpy(sv_type, "none", 5);
+	sv_type = "none";
 #endif /* CONFIG_MMU */
 	seq_printf(f, "mmu\t\t: %s\n", sv_type);
 }