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* [PATCH] aio: Prefer struct_size over open coded arithmetic
@ 2021-09-19  9:45 Len Baker
  2021-09-21  0:11 ` Gustavo A. R. Silva
  0 siblings, 1 reply; 3+ messages in thread
From: Len Baker @ 2021-09-19  9:45 UTC (permalink / raw)
  To: Benjamin LaHaise, Alexander Viro
  Cc: Len Baker, Kees Cook, Gustavo A. R. Silva, linux-aio,
	linux-fsdevel, linux-hardening, linux-kernel

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + size * count" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
---
 fs/aio.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 51b08ab01dff..c2978c0b872c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -659,8 +659,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
 		new_nr = (table ? table->nr : 1) * 4;
 		spin_unlock(&mm->ioctx_lock);

-		table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
-				new_nr, GFP_KERNEL);
+		table = kzalloc(struct_size(table, table, new_nr), GFP_KERNEL);
 		if (!table)
 			return -ENOMEM;

--
2.25.1


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] aio: Prefer struct_size over open coded arithmetic
  2021-09-19  9:45 [PATCH] aio: Prefer struct_size over open coded arithmetic Len Baker
@ 2021-09-21  0:11 ` Gustavo A. R. Silva
  2021-10-20 23:23   ` Gustavo A. R. Silva
  0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-21  0:11 UTC (permalink / raw)
  To: Len Baker, Benjamin LaHaise, Alexander Viro
  Cc: Kees Cook, Gustavo A. R. Silva, linux-aio, linux-fsdevel,
	linux-hardening, linux-kernel



On 9/19/21 04:45, Len Baker wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
> 
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + size * count" in the kzalloc() function.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Signed-off-by: Len Baker <len.baker@gmx.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>  fs/aio.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/aio.c b/fs/aio.c
> index 51b08ab01dff..c2978c0b872c 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -659,8 +659,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
>  		new_nr = (table ? table->nr : 1) * 4;
>  		spin_unlock(&mm->ioctx_lock);
> 
> -		table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
> -				new_nr, GFP_KERNEL);
> +		table = kzalloc(struct_size(table, table, new_nr), GFP_KERNEL);
>  		if (!table)
>  			return -ENOMEM;
> 
> --
> 2.25.1
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] aio: Prefer struct_size over open coded arithmetic
  2021-09-21  0:11 ` Gustavo A. R. Silva
@ 2021-10-20 23:23   ` Gustavo A. R. Silva
  0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2021-10-20 23:23 UTC (permalink / raw)
  To: Gustavo A. R. Silva
  Cc: Len Baker, Benjamin LaHaise, Alexander Viro, Kees Cook,
	linux-aio, linux-fsdevel, linux-hardening, linux-kernel

On Mon, Sep 20, 2021 at 07:11:17PM -0500, Gustavo A. R. Silva wrote:
> 
> 
> On 9/19/21 04:45, Len Baker wrote:
> > As noted in the "Deprecated Interfaces, Language Features, Attributes,
> > and Conventions" documentation [1], size calculations (especially
> > multiplication) should not be performed in memory allocator (or similar)
> > function arguments due to the risk of them overflowing. This could lead
> > to values wrapping around and a smaller allocation being made than the
> > caller was expecting. Using those allocations could lead to linear
> > overflows of heap memory and other misbehaviors.
> > 
> > So, use the struct_size() helper to do the arithmetic instead of the
> > argument "size + size * count" in the kzalloc() function.
> > 
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> > 
> > Signed-off-by: Len Baker <len.baker@gmx.com>
> 
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

I'm taking this in my -next tree.

Thanks, Len.
--
Gustavo

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-10-20 23:18 UTC | newest]

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2021-09-19  9:45 [PATCH] aio: Prefer struct_size over open coded arithmetic Len Baker
2021-09-21  0:11 ` Gustavo A. R. Silva
2021-10-20 23:23   ` Gustavo A. R. Silva

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