CVE-2022-50569

In the Linux kernel, the following vulnerability has been resolved:

xfrm: Update ipcomp_scratches with NULL when freed

Currently if ipcomp_alloc_scratches() fails to allocate memory

ipcomp_scratches holds obsolete address. So when we try to free the

percpu scratches using ipcomp_free_scratches() it tries to vfree non

existent vm area. Described below:

static void * __percpu *ipcomp_alloc_scratches(void)

{

...

scratches = alloc_percpu(void *);

if (!scratches)

return NULL;

ipcomp_scratches does not know about this allocation failure.

Therefore holding the old obsolete address.

...

}

So when we free,

static void ipcomp_free_scratches(void)

{

...

scratches = ipcomp_scratches;

Assigning obsolete address from ipcomp_scratches

if (!scratches)

return;

for_each_possible_cpu(i)

vfree(*per_cpu_ptr(scratches, i));

Trying to free non existent page, causing warning: trying to vfree

existent vm area.

...

}

Fix this breakage by updating ipcomp_scrtches with NULL when scratches

is freed