* [PATCH] afs: Prefer struct_size over open coded arithmetic
@ 2021-09-19 9:44 Len Baker
2021-09-21 0:09 ` Gustavo A. R. Silva
2021-11-02 9:44 ` David Howells
0 siblings, 2 replies; 4+ messages in thread
From: Len Baker @ 2021-09-19 9:44 UTC (permalink / raw)
To: David Howells, Marc Dionne
Cc: Len Baker, Gustavo A. R. Silva, Kees Cook, linux-afs,
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/afs/security.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/afs/security.c b/fs/afs/security.c
index 3c7a8fc4f93f..7c6a63a30394 100644
--- a/fs/afs/security.c
+++ b/fs/afs/security.c
@@ -219,8 +219,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
* yet.
*/
size++;
- new = kzalloc(sizeof(struct afs_permits) +
- sizeof(struct afs_permit) * size, GFP_NOFS);
+ new = kzalloc(struct_size(new, permits, size), GFP_NOFS);
if (!new)
goto out_put;
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] afs: Prefer struct_size over open coded arithmetic
2021-09-19 9:44 [PATCH] afs: Prefer struct_size over open coded arithmetic Len Baker
@ 2021-09-21 0:09 ` Gustavo A. R. Silva
2021-10-20 23:26 ` Gustavo A. R. Silva
2021-11-02 9:44 ` David Howells
1 sibling, 1 reply; 4+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-21 0:09 UTC (permalink / raw)
To: Len Baker, David Howells, Marc Dionne
Cc: Gustavo A. R. Silva, Kees Cook, linux-afs, linux-hardening, linux-kernel
On 9/19/21 04:44, 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/afs/security.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/afs/security.c b/fs/afs/security.c
> index 3c7a8fc4f93f..7c6a63a30394 100644
> --- a/fs/afs/security.c
> +++ b/fs/afs/security.c
> @@ -219,8 +219,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
> * yet.
> */
> size++;
> - new = kzalloc(sizeof(struct afs_permits) +
> - sizeof(struct afs_permit) * size, GFP_NOFS);
> + new = kzalloc(struct_size(new, permits, size), GFP_NOFS);
> if (!new)
> goto out_put;
>
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] afs: Prefer struct_size over open coded arithmetic
2021-09-21 0:09 ` Gustavo A. R. Silva
@ 2021-10-20 23:26 ` Gustavo A. R. Silva
0 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2021-10-20 23:26 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Len Baker, David Howells, Marc Dionne, Kees Cook, linux-afs,
linux-hardening, linux-kernel
On Mon, Sep 20, 2021 at 07:09:38PM -0500, Gustavo A. R. Silva wrote:
>
>
> On 9/19/21 04:44, 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] 4+ messages in thread
* Re: [PATCH] afs: Prefer struct_size over open coded arithmetic
2021-09-19 9:44 [PATCH] afs: Prefer struct_size over open coded arithmetic Len Baker
2021-09-21 0:09 ` Gustavo A. R. Silva
@ 2021-11-02 9:44 ` David Howells
1 sibling, 0 replies; 4+ messages in thread
From: David Howells @ 2021-11-02 9:44 UTC (permalink / raw)
To: Len Baker
Cc: dhowells, Marc Dionne, Gustavo A. R. Silva, Kees Cook, linux-afs,
linux-hardening, linux-kernel
Len Baker <len.baker@gmx.com> 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>
Acked-by: David Howells <dhowells@redhat.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-09-21 0:09 ` Gustavo A. R. Silva
2021-10-20 23:26 ` Gustavo A. R. Silva
2021-11-02 9:44 ` David Howells
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