Merge: CVE-2024-57977: memcg: fix soft lockup in the OOM process

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1014

JIRA: https://issues.redhat.com/browse/RHEL-81199
CVE: CVE-2024-57977

```
commit ade8147
Author: Chen Ridong <chenridong@huawei.com>
Date:   Tue Dec 24 02:52:38 2024 +0000

    memcg: fix soft lockup in the OOM process

    A soft lockup issue was found in the product with about 56,000 tasks were
    in the OOM cgroup, it was traversing them when the soft lockup was
    triggered.

    watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [VM Thread:1503066]
    CPU: 2 PID: 1503066 Comm: VM Thread Kdump: loaded Tainted: G
    Hardware name: Huawei Cloud OpenStack Nova, BIOS
    RIP: 0010:console_unlock+0x343/0x540
    RSP: 0000:ffffb751447db9a0 EFLAGS: 00000247 ORIG_RAX: ffffffffffffff13
    RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00000000ffffffff
    RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000247
    RBP: ffffffffafc71f90 R08: 0000000000000000 R09: 0000000000000040
    R10: 0000000000000080 R11: 0000000000000000 R12: ffffffffafc74bd0
    R13: ffffffffaf60a220 R14: 0000000000000247 R15: 0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007f2fe6ad91f0 CR3: 00000004b2076003 CR4: 0000000000360ee0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     vprintk_emit+0x193/0x280
     printk+0x52/0x6e
     dump_task+0x114/0x130
     mem_cgroup_scan_tasks+0x76/0x100
     dump_header+0x1fe/0x210
     oom_kill_process+0xd1/0x100
     out_of_memory+0x125/0x570
     mem_cgroup_out_of_memory+0xb5/0xd0
     try_charge+0x720/0x770
     mem_cgroup_try_charge+0x86/0x180
     mem_cgroup_try_charge_delay+0x1c/0x40
     do_anonymous_page+0xb5/0x390
     handle_mm_fault+0xc4/0x1f0

    This is because thousands of processes are in the OOM cgroup, it takes a
    long time to traverse all of them.  As a result, this lead to soft lockup
    in the OOM process.

    To fix this issue, call 'cond_resched' in the 'mem_cgroup_scan_tasks'
    function per 1000 iterations.  For global OOM, call
    'touch_softlockup_watchdog' per 1000 iterations to avoid this issue.

    Link: https://lkml.kernel.org/r/20241224025238.3768787-1-chenridong@huaweicloud.com
    Fixes: 9cbb78b ("mm, memcg: introduce own oom handler to iterate only over its own threads")
    Signed-off-by: Chen Ridong <chenridong@huawei.com>
    Acked-by: Michal Hocko <mhocko@suse.com>
    Cc: Roman Gushchin <roman.gushchin@linux.dev>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Shakeel Butt <shakeelb@google.com>
    Cc: Muchun Song <songmuchun@bytedance.com>
    Cc: Michal Koutný <mkoutny@suse.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>```

Signed-off-by: Radostin Stoyanov <rstoyano@redhat.com>

Approved-by: Waiman Long <longman@redhat.com>
Approved-by: Herton R. Krzesinski <herton@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Julio Faracco <jfaracco@redhat.com>

Author: jcfaracco

mm/memcontrol.c

@@ -1203,8 +1203,11 @@ void mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
 		struct task_struct *task;
 
 		css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it);
-		while (!ret && (task = css_task_iter_next(&it)))
+		while (!ret && (task = css_task_iter_next(&it))) {
 			ret = fn(task, arg);
+			/* Avoid potential softlockup warning */
+			cond_resched();
+		}
 		css_task_iter_end(&it);
 		if (ret) {
 			mem_cgroup_iter_break(memcg, iter);

mm/oom_kill.c

@@ -44,6 +44,7 @@
 #include <linux/init.h>
 #include <linux/mmu_notifier.h>
 #include <linux/cred.h>
+#include <linux/nmi.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -430,10 +431,15 @@ static void dump_tasks(struct oom_control *oc)
 		mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
 	else {
 		struct task_struct *p;
+		int i = 0;
 
 		rcu_read_lock();
-		for_each_process(p)
+		for_each_process(p) {
+			/* Avoid potential softlockup warning */
+			if ((++i & 1023) == 0)
+				touch_softlockup_watchdog();
 			dump_task(p, oc);
+		}
 		rcu_read_unlock();
 	}
 }