CVE-2024-40899 Information

Description

In the Linux kernel the following vulnerability has been resolved:

cachefiles: fix slab-use-after-free in cachefiles_ondemand_get_fd()

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+0x609/0xab0 Write of size 4 at addr ffff888109164a80 by task ondemand-04-dae/4962

CPU: 11 PID: 4962 Comm: ondemand-04-dae Not tainted 6.8.0-rc7-dirty 542 Call Trace: kasan_report+0x94/0xc0 cachefiles_ondemand_daemon_read+0x609/0xab0 vfs_read+0x169/0xb50 ksys_read+0xf5/0x1e0

Allocated by task 626: __kmalloc+0x1df/0x4b0 cachefiles_ondemand_send_req+0x24d/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 […]

Freed by task 626: kfree+0xf1/0x2c0 cachefiles_ondemand_send_req+0x568/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 […]

Following is the process that triggers the issue:

 mount  |   daemon_thread1    |    daemon_thread2

cachefiles_ondemand_init_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
          cachefiles_ondemand_get_fd
          copy_to_user(_buffer msg n)
        process_open_req(REQ_A)
                              ------ 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

         write(devfd (## Reference

https://git.kernel.org/stable/c/99e9c5bd27ddefa0f9db88625bf5e31c1e833d62 https://git.kernel.org/stable/c/a6de82765e12fb1201ab607f0d3ffe3309b30fc0 https://git.kernel.org/stable/c/1d902d9a3aa4f2a8bda698294e34be788be012fc https://git.kernel.org/stable/c/de3e26f9e5b76fc628077578c001c4a51bf54d06