CVE-2024-39510 cachefiles: fix slab-use-after-free in cachefiles_ondemand_daemon_read()
A use-after-free flaw in the Linux kernel's cachefiles subsystem allows local attackers to potentially execute arbitrary code or escalate privileges.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-39510?
CVE-2024-39510 is a high-severity use after free vulnerability in Linux kernel, published on 12 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
cachefiles: fix slab-use-after-free in cachefiles_ondemand_daemon_read()
We got the following issue in a fuzz test of randomly issuing the restore command:
================================================================== BUG: KASAN: slab-use-after-free in cachefiles_ondemand_daemon_read+0xb41/0xb60 Read of size 8 at addr ffff888122e84088 by task ondemand-04-dae/963
CPU: 13 PID: 963 Comm: ondemand-04-dae Not tainted 6.8.0-dirty #564 Call Trace: kasan_report+0x93/0xc0 cachefiles_ondemand_daemon_read+0xb41/0xb60 vfs_read+0x169/0xb50 ksys_read+0xf5/0x1e0
Allocated by task 116: kmem_cache_alloc+0x140/0x3a0 cachefiles_lookup_cookie+0x140/0xcd0 fscache_cookie_state_machine+0x43c/0x1230 [...]
Freed by task 792: kmem_cache_free+0xfe/0x390 cachefiles_put_object+0x241/0x480 fscache_cookie_state_machine+0x5c8/0x1230 [...] ==================================================================
Following is the process that triggers the issue:
mount | daemon_thread1 | daemon_thread2 ------------------------------------------------------------ cachefiles_withdraw_cookie cachefiles_ondemand_clean_object(object) cachefiles_ondemand_send_req REQ_A = kzalloc(sizeof(*req) + data_len) wait_for_completion(&REQ_A->done)
cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req msg->object_id = req->object->ondemand->ondemand_id ------ restore ------ cachefiles_ondemand_restore xas_for_each(&xas, req, ULONG_MAX) xas_set_mark(&xas, CACHEFILES_REQ_NEW)
cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req copy_to_user(_buffer, msg, n) xa_erase(&cache->reqs, id) complete(&REQ_A->done) ------ close(fd) ------ cachefiles_ondemand_fd_release cachefiles_put_object cachefiles_put_object kmem_cache_free(cachefiles_object_jar, object) REQ_A->object->ondemand->ondemand_id // object UAF !!!
When we see the request within xa_lock, req->object must not have been freed yet, so grab the reference count of object before xa_unlock to avoid the above issue.
Weakness: CWE-416
Which versions are affected by CVE-2024-39510?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-39510?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-39510 being exploited?
There is no known exploitation of CVE-2024-39510 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-39510, DEBIAN-CVE-2024-39510, GHSA-77p5-68v4-943h, UBUNTU-CVE-2024-39510.