GHSA-W39W-J699-C6W4
Vulnerability from github – Published: 2024-08-22 03:31 – Updated: 2024-09-12 15:32In the Linux kernel, the following vulnerability has been resolved:
sched/fair: Fix fault in reweight_entity
Syzbot found a GPF in reweight_entity. This has been bisected to commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
There is a race between sched_post_fork() and setpriority(PRIO_PGRP) within a thread group that causes a null-ptr-deref in reweight_entity() in CFS. The scenario is that the main process spawns number of new threads, which then call setpriority(PRIO_PGRP, 0, -20), wait, and exit. For each of the new threads the copy_process() gets invoked, which adds the new task_struct and calls sched_post_fork() for it.
In the above scenario there is a possibility that setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread in the group that is just being created by copy_process(), and for which the sched_post_fork() has not been executed yet. This will trigger a null pointer dereference in reweight_entity(), as it will try to access the run queue pointer, which hasn't been set.
Before the mentioned change the cfs_rq pointer for the task has been set in sched_fork(), which is called much earlier in copy_process(), before the new task is added to the thread_group. Now it is done in the sched_post_fork(), which is called after that. To fix the issue the remove the update_load param from the update_load param() function and call reweight_task() only if the task flag doesn't have the TASK_NEW flag set.
{
"affected": [],
"aliases": [
"CVE-2022-48921"
],
"database_specific": {
"cwe_ids": [
"CWE-362"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-08-22T02:15:08Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Fix fault in reweight_entity\n\nSyzbot found a GPF in reweight_entity. This has been bisected to\ncommit 4ef0c5c6b5ba (\"kernel/sched: Fix sched_fork() access an invalid\nsched_task_group\")\n\nThere\u00a0is a race between sched_post_fork() and setpriority(PRIO_PGRP)\nwithin a thread group that causes a null-ptr-deref\u00a0in\nreweight_entity() in CFS. The scenario is that the main process spawns\nnumber of new threads, which then call setpriority(PRIO_PGRP, 0, -20),\nwait, and exit. For each of the new threads the copy_process() gets\ninvoked, which adds the new task_struct and calls sched_post_fork()\nfor it.\n\nIn the above scenario there is a possibility that\nsetpriority(PRIO_PGRP) and set_one_prio() will be called for a thread\nin the group that is just being created by copy_process(), and for\nwhich the sched_post_fork() has not been executed yet. This will\ntrigger a null pointer dereference in reweight_entity(),\u00a0as it will\ntry to access the run queue pointer, which hasn\u0027t been set.\n\nBefore the mentioned change the cfs_rq pointer for the task has been\nset in sched_fork(), which is called much earlier in copy_process(),\nbefore the new task is added to the thread_group. Now it is done in\nthe sched_post_fork(), which is called after that. To fix the issue\nthe remove the update_load param from the update_load param() function\nand call reweight_task() only if the task flag doesn\u0027t have the\nTASK_NEW flag set.",
"id": "GHSA-w39w-j699-c6w4",
"modified": "2024-09-12T15:32:59Z",
"published": "2024-08-22T03:31:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-48921"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/13765de8148f71fa795e0a6607de37c49ea5915a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/589a954daab5e18399860b6c8ffaeaf79844eb20"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8f317cd888059c59e2fa924bf4b0957cfa53f78e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e0bcd6b5779352aed88f2e538a82a39f1a7715bb"
}
],
"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"
}
]
}
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