# CVE-2024-40915: linux: In the Linux kernel, the following vulnerability has been resolved:  riscv: rewrite __kernel_map_pages() to fix sleep...

CVE-2024-40915 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-40915, released July 12, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-40915
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 12, 2024

## 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>] dump_stack_lvl+0x5a/0x72 [<ffffffff8092bb24>] dump_stack+0x14/0x1c [<ffffffff8003b7ac>] __might_resched+0x104/0x10e [<ffffffff8003b7f4>] __might_sleep+0x3e/0x62 [<ffffffff8093276a>] down_write+0x20/0x72 [<ffffffff8000cf00>] __set_memory+0x82/0x2fa [<ffffffff8000d324>] __kernel_map_pages+0x5a/0xd4 [<ffffffff80196cca>] __alloc_pages_bulk+0x3b2/0x43a [<ffffffff8018ee82>] __vmalloc_node_range+0x196/0x6ba [<ffffffff80011904>] copy_process+0x72c/0x17ec [<ffffffff80012ab4>] kernel_clone+0x60/0x2fe [<ffffffff80012f62>] kernel_thread+0x82/0xa0 [<ffffffff8003552c>] kthreadd+0x14a/0x1be [<ffffffff809357de>] ret_from_fork+0xe/0x1c  Rewrite this function with apply_to_existing_page_range(). It is fine to not have any locking, because __kernel_map_pages() works with pages being allocated/deallocated and those pages are not changed by anyone else in the meantime.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.99-1 | [DEBIAN-CVE-2024-40915](https://patchblox.com/security/data/fix/linux/debian-cve-2024-40915.md) | Jul 12, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.9.7-1 | [DEBIAN-CVE-2024-40915](https://patchblox.com/security/data/fix/linux/debian-cve-2024-40915.md) | Jul 12, 2024 |
| Linux | linux Debian 14 | 6.9.7-1 | [DEBIAN-CVE-2024-40915](https://patchblox.com/security/data/fix/linux/debian-cve-2024-40915.md) | Jul 12, 2024 |

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