Description

In the Linux kernel, the following vulnerability has been resolved: cachefiles: cyclic allocation of msg_id to avoid reuse Reusing the msg_id after a maliciously completed reopen request may cause a read request to remain unprocessed and result in a hung, as shown below: t1 | t2 | t3 ------------------------------------------------- cachefiles_ondemand_select_req cachefiles_ondemand_object_is_close(A) cachefiles_ondemand_set_object_reopening(A) queue_work(fscache_object_wq, &info->work) ondemand_object_worker cachefiles_ondemand_init_object(A) cachefiles_ondemand_send_req(OPEN) // get msg_id 6 wait_for_completion(&req_A->done) cachefiles_ondemand_daemon_read // read msg_id 6 req_A cachefiles_ondemand_get_fd copy_to_user // Malicious completion msg_id 6 copen 6,-1 cachefiles_ondemand_copen complete(&req_A->done) // will not set the object to close // because ondemand_id && fd is valid. // ondemand_object_worker() is done // but the object is still reopening. // new open req_B cachefiles_ondemand_init_object(B) cachefiles_ondemand_send_req(OPEN) // reuse msg_id 6 process_open_req copen 6,A.size // The expected failed copen was executed successfully Expect copen to fail, and when it does, it closes fd, which sets the object to close, and then close triggers reopen again. However, due to msg_id reuse resulting in a successful copen, the anonymous fd is not closed until the daemon exits. Therefore read requests waiting for reopen to complete may trigger hung task. To avoid this issue, allocate the msg_id cyclically to avoid reusing the msg_id for a very short duration of time.

Weaknesses 1

Affected Products 10

References 5

• git.kernel.org https://git.kernel.org/stable/c/19f4f399091478c95947f6bd7ad61622300c30d9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/35710c6c4a1c64478ec1b5e0e81d386c0844dec6
  Patch
• git.kernel.org https://git.kernel.org/stable/c/9d3bf4e9aa23f0d9e99ebe7a94f232ddba54ee17
  Patch
• git.kernel.org https://git.kernel.org/stable/c/de045a82e1a4e04be62718d3c2981a55150765a0
  Patch
• lists.debian.org https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html

Remediation

• git.kernel.org https://git.kernel.org/stable/c/19f4f399091478c95947f6bd7ad61622300c30d9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/35710c6c4a1c64478ec1b5e0e81d386c0844dec6
  Patch
• git.kernel.org https://git.kernel.org/stable/c/9d3bf4e9aa23f0d9e99ebe7a94f232ddba54ee17
  Patch
• git.kernel.org https://git.kernel.org/stable/c/de045a82e1a4e04be62718d3c2981a55150765a0
  Patch