{"id":"CVE-2024-50082","summary":"blk-rq-qos: fix crash on rq_qos_wait vs. rq_qos_wake_function race","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nblk-rq-qos: fix crash on rq_qos_wait vs. rq_qos_wake_function race\n\nWe're seeing crashes from rq_qos_wake_function that look like this:\n\n  BUG: unable to handle page fault for address: ffffafe180a40084\n  #PF: supervisor write access in kernel mode\n  #PF: error_code(0x0002) - not-present page\n  PGD 100000067 P4D 100000067 PUD 10027c067 PMD 10115d067 PTE 0\n  Oops: Oops: 0002 [#1] PREEMPT SMP PTI\n  CPU: 17 UID: 0 PID: 0 Comm: swapper/17 Not tainted 6.12.0-rc3-00013-geca631b8fe80 #11\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014\n  RIP: 0010:_raw_spin_lock_irqsave+0x1d/0x40\n  Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 54 9c 41 5c fa 65 ff 05 62 97 30 4c 31 c0 ba 01 00 00 00 \u003cf0\u003e 0f b1 17 75 0a 4c 89 e0 41 5c c3 cc cc cc cc 89 c6 e8 2c 0b 00\n  RSP: 0018:ffffafe180580ca0 EFLAGS: 00010046\n  RAX: 0000000000000000 RBX: ffffafe180a3f7a8 RCX: 0000000000000011\n  RDX: 0000000000000001 RSI: 0000000000000003 RDI: ffffafe180a40084\n  RBP: 0000000000000000 R08: 00000000001e7240 R09: 0000000000000011\n  R10: 0000000000000028 R11: 0000000000000888 R12: 0000000000000002\n  R13: ffffafe180a40084 R14: 0000000000000000 R15: 0000000000000003\n  FS:  0000000000000000(0000) GS:ffff9aaf1f280000(0000) knlGS:0000000000000000\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  CR2: ffffafe180a40084 CR3: 000000010e428002 CR4: 0000000000770ef0\n  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n  PKRU: 55555554\n  Call Trace:\n   \u003cIRQ\u003e\n   try_to_wake_up+0x5a/0x6a0\n   rq_qos_wake_function+0x71/0x80\n   __wake_up_common+0x75/0xa0\n   __wake_up+0x36/0x60\n   scale_up.part.0+0x50/0x110\n   wb_timer_fn+0x227/0x450\n   ...\n\nSo rq_qos_wake_function() calls wake_up_process(data-\u003etask), which calls\ntry_to_wake_up(), which faults in raw_spin_lock_irqsave(&p-\u003epi_lock).\n\np comes from data-\u003etask, and data comes from the waitqueue entry, which\nis stored on the waiter's stack in rq_qos_wait(). Analyzing the core\ndump with drgn, I found that the waiter had already woken up and moved\non to a completely unrelated code path, clobbering what was previously\ndata-\u003etask. Meanwhile, the waker was passing the clobbered garbage in\ndata-\u003etask to wake_up_process(), leading to the crash.\n\nWhat's happening is that in between rq_qos_wake_function() deleting the\nwaitqueue entry and calling wake_up_process(), rq_qos_wait() is finding\nthat it already got a token and returning. The race looks like this:\n\nrq_qos_wait()                           rq_qos_wake_function()\n==============================================================\nprepare_to_wait_exclusive()\n                                        data-\u003egot_token = true;\n                                        list_del_init(&curr-\u003eentry);\nif (data.got_token)\n        break;\nfinish_wait(&rqw-\u003ewait, &data.wq);\n  ^- returns immediately because\n     list_empty_careful(&wq_entry-\u003eentry)\n     is true\n... return, go do something else ...\n                                        wake_up_process(data-\u003etask)\n                                          (NO LONGER VALID!)-^\n\nNormally, finish_wait() is supposed to synchronize against the waker.\nBut, as noted above, it is returning immediately because the waitqueue\nentry has already been removed from the waitqueue.\n\nThe bug is that rq_qos_wake_function() is accessing the waitqueue entry\nAFTER deleting it. Note that autoremove_wake_function() wakes the waiter\nand THEN deletes the waitqueue entry, which is the proper order.\n\nFix it by swapping the order. We also need to use\nlist_del_init_careful() to match the list_empty_careful() in\nfinish_wait().","modified":"2026-03-20T12:39:34.264701Z","published":"2024-10-29T00:50:24.667Z","related":["ALSA-2024:10943","ALSA-2024:10944","SUSE-SU-2024:4314-1","SUSE-SU-2024:4315-1","SUSE-SU-2024:4316-1","SUSE-SU-2024:4318-1","SUSE-SU-2024:4364-1","SUSE-SU-2024:4376-1","SUSE-SU-2024:4387-1","SUSE-SU-2025:20163-1","SUSE-SU-2025:20164-1","SUSE-SU-2025:20246-1","SUSE-SU-2025:20247-1","USN-7276-1","USN-7277-1","openSUSE-SU-2024:14500-1","openSUSE-SU-2025:14705-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/50xxx/CVE-2024-50082.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/04f283fc16c8d5db641b6bffd2d8310aa7eccebc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3bc6d0f8b70a9101456cf02ab99acb75254e1852"},{"type":"WEB","url":"https://git.kernel.org/stable/c/455a469758e57a6fe070e3e342db12e4a629e0eb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4c5b123ab289767afe940389dbb963c5c05e594e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b5e900a3612b69423a0e1b0ab67841a1fb4af80f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d04b72c9ef2b0689bfc1057d21c4aeed087c329f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e972b08b91ef48488bae9789f03cfedb148667fb"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/50xxx/CVE-2024-50082.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-50082"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"38cfb5a45ee013bfab5d1ae4c4738815e744b440"},{"fixed":"d04b72c9ef2b0689bfc1057d21c4aeed087c329f"},{"fixed":"3bc6d0f8b70a9101456cf02ab99acb75254e1852"},{"fixed":"455a469758e57a6fe070e3e342db12e4a629e0eb"},{"fixed":"b5e900a3612b69423a0e1b0ab67841a1fb4af80f"},{"fixed":"4c5b123ab289767afe940389dbb963c5c05e594e"},{"fixed":"04f283fc16c8d5db641b6bffd2d8310aa7eccebc"},{"fixed":"e972b08b91ef48488bae9789f03cfedb148667fb"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-50082.json"}}],"schema_version":"1.7.5"}