ghsa-58q9-jhx4-mj9p
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
blk-rq-qos: fix crash on rq_qos_wait vs. rq_qos_wake_function race
We're seeing crashes from rq_qos_wake_function that look like this:
BUG: unable to handle page fault for address: ffffafe180a40084
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 100000067 P4D 100000067 PUD 10027c067 PMD 10115d067 PTE 0
Oops: Oops: 0002 [#1] PREEMPT SMP PTI
CPU: 17 UID: 0 PID: 0 Comm: swapper/17 Not tainted 6.12.0-rc3-00013-geca631b8fe80 #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
RIP: 0010:_raw_spin_lock_irqsave+0x1d/0x40
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
So rq_qos_wake_function() calls wake_up_process(data->task), which calls try_to_wake_up(), which faults in raw_spin_lock_irqsave(&p->pi_lock).
p comes from data->task, and data comes from the waitqueue entry, which is stored on the waiter's stack in rq_qos_wait(). Analyzing the core dump with drgn, I found that the waiter had already woken up and moved on to a completely unrelated code path, clobbering what was previously data->task. Meanwhile, the waker was passing the clobbered garbage in data->task to wake_up_process(), leading to the crash.
What's happening is that in between rq_qos_wake_function() deleting the waitqueue entry and calling wake_up_process(), rq_qos_wait() is finding that it already got a token and returning. The race looks like this:
rq_qos_wait() rq_qos_wake_function()
prepare_to_wait_exclusive() data->got_token = true; list_del_init(&curr->entry); if (data.got_token) break; finish_wait(&rqw->wait, &data.wq); ^- returns immediately because list_empty_careful(&wq_entry->entry) is true ... return, go do something else ... wake_up_process(data->task) (NO LONGER VALID!)-^
Normally, finish_wait() is supposed to synchronize against the waker. But, as noted above, it is returning immediately because the waitqueue entry has already been removed from the waitqueue.
The bug is that rq_qos_wake_function() is accessing the waitqueue entry AFTER deleting it. Note that autoremove_wake_function() wakes the waiter and THEN deletes the waitqueue entry, which is the proper order.
Fix it by swapping the order. We also need to use list_del_init_careful() to match the list_empty_careful() in finish_wait().
{
"affected": [],
"aliases": [
"CVE-2024-50082"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-29T01:15:05Z",
"severity": "MODERATE"
},
"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\u0027re 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(\u0026p-\u003epi_lock).\n\np comes from data-\u003etask, and data comes from the waitqueue entry, which\nis stored on the waiter\u0027s 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\u0027s 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(\u0026curr-\u003eentry);\nif (data.got_token)\n break;\nfinish_wait(\u0026rqw-\u003ewait, \u0026data.wq);\n ^- returns immediately because\n list_empty_careful(\u0026wq_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().",
"id": "GHSA-58q9-jhx4-mj9p",
"modified": "2024-11-08T18:30:47Z",
"published": "2024-10-29T03:31:06Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-50082"
},
{
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.