| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-41050: cachefiles: cyclic allocation of msg_id to avoid reuse |
| |
| 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. |
| |
| The Linux kernel CVE team has assigned CVE-2024-41050 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.19 with commit c8383054506c77b814489c09877b5db83fd4abf2 and fixed in 6.1.100 with commit 35710c6c4a1c64478ec1b5e0e81d386c0844dec6 |
| Issue introduced in 5.19 with commit c8383054506c77b814489c09877b5db83fd4abf2 and fixed in 6.6.41 with commit de045a82e1a4e04be62718d3c2981a55150765a0 |
| Issue introduced in 5.19 with commit c8383054506c77b814489c09877b5db83fd4abf2 and fixed in 6.9.10 with commit 9d3bf4e9aa23f0d9e99ebe7a94f232ddba54ee17 |
| Issue introduced in 5.19 with commit c8383054506c77b814489c09877b5db83fd4abf2 and fixed in 6.10 with commit 19f4f399091478c95947f6bd7ad61622300c30d9 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-41050 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| fs/cachefiles/internal.h |
| fs/cachefiles/ondemand.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/35710c6c4a1c64478ec1b5e0e81d386c0844dec6 |
| https://git.kernel.org/stable/c/de045a82e1a4e04be62718d3c2981a55150765a0 |
| https://git.kernel.org/stable/c/9d3bf4e9aa23f0d9e99ebe7a94f232ddba54ee17 |
| https://git.kernel.org/stable/c/19f4f399091478c95947f6bd7ad61622300c30d9 |
