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>

diff --git a/fs/afs/security.c b/fs/afs/security.c
index 3c7a8fc4f93f762392f452f6e74debc004d6fead..7c6a63a303940527abf16f23d76193960576f2ef 100644 (file)
--- 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;