CVE-2024-40915

/// Technical description

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

riscv: rewrite __kernel_map_pages() to fix sleeping in invalid context

__kernel_map_pages() is a debug function which clears the valid bit in page

table entry for deallocated pages to detect illegal memory accesses to

freed pages.

This function set/clear the valid bit using __set_memory(). __set_memory()

acquires init_mm's semaphore, and this operation may sleep. This is

problematic, because __kernel_map_pages() can be called in atomic context,

and thus is illegal to sleep. An example warning that this causes:

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1578

in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2, name: kthreadd

preempt_count: 2, expected: 0

CPU: 0 PID: 2 Comm: kthreadd Not tainted 6.9.0-g1d4c6d784ef6 #37

Hardware name: riscv-virtio,qemu (DT)

Call Trace:

[<ffffffff800060dc>] dump_backtrace+0x1c/0x24

[<ffffffff8091ef6e>] show_stack+0x2c/0x38

[<ffffffff8092baf8>] du

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References