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afs: Prefer struct_size over open coded arithmetic 

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>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
This commit is contained in:
Len Baker 2021-09-19 11:44:32 +02:00 committed by Gustavo A. R. Silva
parent ce522ba9ef
commit cc68c613d6
1 changed files with 1 additions and 2 deletions
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3
fs/afs/security.c
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@ -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;