CVE-2024-45020

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

bpf: Fix a kernel verifier crash in stacksafe()

Daniel Hodges reported a kernel verifier crash when playing with sched-ext.

Further investigation shows that the crash is due to invalid memory access

in stacksafe(). More specifically, it is the following code:

if (exact != NOT_EXACT &&

old->stack[spi].slot_type[i % BPF_REG_SIZE] !=

cur->stack[spi].slot_type[i % BPF_REG_SIZE])

return false;

The 'i' iterates old->allocated_stack.

If cur->allocated_stack < old->allocated_stack the out-of-bound

access will happen.

To fix the issue add 'i >= cur->allocated_stack' check such that if

the condition is true, stacksafe() should fail. Otherwise,

cur->stack[spi].slot_type[i % BPF_REG_SIZE] memory access is legal.