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

diff --git a/fs/aio.c b/fs/aio.c
index 51b08ab01dffc36d649d3e8285a52fc6a3e8ed66..c2978c0b872c8bae52001ad16e25ba361a302c79 100644 (file)
--- 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;