CVE-2022-50569

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

xfrm: Update ipcomp_scratches with NULL when freed

Currently if ipcompallocscratches() fails to allocate memory ipcompscratches holds obsolete address. So when we try to free the percpu scratches using ipcompfree_scratches() it tries to vfree non existent vm area. Described below:

static void * _percpu *ipcompallocscratches(void) { ... scratches = allocpercpu(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 ipcompfreescratches(void) { ... scratches = ipcompscratches; Assigning obsolete address from ipcompscratches

    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