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Message-ID: <2024072927-CVE-2024-41050-f3ff@gregkh> Date: Mon, 29 Jul 2024 16:32:45 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.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 c8383054506c and fixed in 6.1.100 with commit 35710c6c4a1c Issue introduced in 5.19 with commit c8383054506c and fixed in 6.6.41 with commit de045a82e1a4 Issue introduced in 5.19 with commit c8383054506c and fixed in 6.9.10 with commit 9d3bf4e9aa23 Issue introduced in 5.19 with commit c8383054506c and fixed in 6.10 with commit 19f4f3990914 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
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