On 11/4/2021 2:25 AM, Greg KH wrote:
On Wed, Nov 03, 2021 at 02:01:42PM -0500, George Kennedy wrote:
Change return checks from kcalloc() to now check for NULL and
ZERO_SIZE_PTR using the ZERO_OR_NULL_PTR macro or the following
crash can occur if ZERO_SIZE_PTR indicator is returned.
That seems really broken in the api, why is kcalloc() returning
ZERO_SIZE_PTR?
See Dan Carpenter's explanation.
kcalloc() purposely returns ZERO_SIZE_PTR if its size arg is zero.
See commit: 6cb8f91320d3e720351c21741da795fed580b21b
Please fix that, otherwise you need to fix all callers in the kernel
tree.
Here are the kcalloc() args:
/**
* kcalloc - allocate memory for an array. The memory is set to zero.
* @n: number of elements.
* @size: element size.
* @flags: the type of memory to allocate (see kmalloc).
*/
static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
Any call to kcalloc() where the size arg (the 2nd arg) can possibly be
zero needs to check for ZERO_SIZE_PTR being returned along with checking
for NULL being returned, which the ZERO_OR_NULL_PTR macro does.
In most cases throughout the kernel the calls to kcalloc() are with the
size arg set to a sizeof some data structure, so ZERO_SIZE_PTR will not
be returned and a following check for NULL being returned is all that is
needed.
Thank you,
George
thanks,
greg k-h
