{"id":"CVE-2022-49540","url":"https://www.cyber-defence.io/tools/cve/CVE-2022-49540","generatedAt":"2026-10-27T17:45:17.226Z","title":"In the Linux kernel, the following vulnerability has been resolved: rcu-tasks: Fix race in schedule and flush work While booting secondary CPUs, cpus_read_[lock/unlock] is not keeping online cpumask stable.","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nrcu-tasks: Fix race in schedule and flush work\n\nWhile booting secondary CPUs, cpus_read_[lock/unlock] is not keeping\nonline cpumask stable. The transient online mask results in below\ncalltrace.\n\n[ 0.324121] CPU1: Booted secondary processor 0x0000000001 [0x410fd083]\n[ 0.346652] Detected PIPT I-cache on CPU2\n[ 0.347212] CPU2: Booted secondary processor 0x0000000002 [0x410fd083]\n[ 0.377255] Detected PIPT I-cache on CPU3\n[ 0.377823] CPU3: Booted secondary processor 0x0000000003 [0x410fd083]\n[ 0.379040] ------------[ cut here ]------------\n[ 0.383662] WARNING: CPU: 0 PID: 10 at kernel/workqueue.c:3084 __flush_work+0x12c/0x138\n[ 0.384850] Modules linked in:\n[ 0.385403] CPU: 0 PID: 10 Comm: rcu_tasks_rude_ Not tainted 5.17.0-rc3-v8+ #13\n[ 0.386473] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT)\n[ 0.387289] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)\n[ 0.388308] pc : __flush_work+0x12c/0x138\n[ 0.388970] lr : __flush_work+0x80/0x138\n[ 0.389620] sp : ffffffc00aaf3c60\n[ 0.390139] x29: ffffffc00aaf3d20 x28: ffffffc009c16af0 x27: ffffff80f761df48\n[ 0.391316] x26: 0000000000000004 x25: 0000000000000003 x24: 0000000000000100\n[ 0.392493] x23: ffffffffffffffff x22: ffffffc009c16b10 x21: ffffffc009c16b28\n[ 0.393668] x20: ffffffc009e53861 x19: ffffff80f77fbf40 x18: 00000000d744fcc9\n[ 0.394842] x17: 000000000000000b x16: 00000000000001c2 x15: ffffffc009e57550\n[ 0.396016] x14: 0000000000000000 x13: ffffffffffffffff x12: 0000000100000000\n[ 0.397190] x11: 0000000000000462 x10: ffffff8040258008 x9 : 0000000100000000\n[ 0.398364] x8 : 0000000000000000 x7 : ffffffc0093c8bf4 x6 : 0000000000000000\n[ 0.399538] x5 : 0000000000000000 x4 : ffffffc00a976e40 x3 : ffffffc00810444c\n[ 0.400711] x2 : 0000000000000004 x1 : 0000000000000000 x0 : 0000000000000000\n[ 0.401886] Call trace:\n[ 0.402309] __flush_work+0x12c/0x138\n[ 0.402941] schedule_on_each_cpu+0x228/0x278\n[ 0.403693] rcu_tasks_rude_wait_gp+0x130/0x144\n[ 0.404502] rcu_tasks_kthread+0x220/0x254\n[ 0.405264] kthread+0x174/0x1ac\n[ 0.405837] ret_from_fork+0x10/0x20\n[ 0.406456] irq event stamp: 102\n[ 0.406966] hardirqs last enabled at (101): [] _raw_spin_unlock_irq+0x78/0xb4\n[ 0.408304] hardirqs last disabled at (102): [] el1_dbg+0x24/0x5c\n[ 0.409410] softirqs last enabled at (54): [] local_bh_enable+0xc/0x2c\n[ 0.410645] softirqs last disabled at (50): [] local_bh_disable+0xc/0x2c\n[ 0.411890] ---[ end trace 0000000000000000 ]---\n[ 0.413000] smp: Brought up 1 node, 4 CPUs\n[ 0.413762] SMP: Total of 4 processors activated.\n[ 0.414566] CPU features: detected: 32-bit EL0 Support\n[ 0.415414] CPU features: detected: 32-bit EL1 Support\n[ 0.416278] CPU features: detected: CRC32 instructions\n[ 0.447021] Callback from call_rcu_tasks_rude() invoked.\n[ 0.506693] Callback from call_rcu_tasks() invoked.\n\nThis commit therefore fixes this issue by applying a single-CPU\noptimization to the RCU Tasks Rude grace-period process. The key point\nhere is that the purpose of this RCU flavor is to force a schedule on\neach online CPU since some past event. But the rcu_tasks_rude_wait_gp()\nfunction runs in the context of the RCU Tasks Rude's grace-period kthread,\nso there must already have been a context switch on the current CPU since\nthe call to either synchronize_rcu_tasks_rude() or call_rcu_tasks_rude().\nSo if there is only a single CPU online, RCU Tasks Rude's grace-period\nkthread does not need to anything at all.\n\nIt turns out that the rcu_tasks_rude_wait_gp() function's call to\nschedule_on_each_cpu() causes problems during early boot. During that\ntime, there is only one online CPU, namely the boot CPU. Therefore,\napplying this single-CPU optimization fixes early-boot instances of\nthis problem.","published":"2025-02-26T07:01:30.000Z","lastModified":"2026-06-17T05:18:23.000Z","status":"Analyzed","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":4.7,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-362"],"affected":["linux/linux kernel"],"epss":{"score":0.00188,"percentile":0.08352,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.19%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/1c6c3f2336642fb3074593911f5176565f47ec41","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/230bf5878af6038dfb63d9184272a58475236580","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8f49a8758b5cd541bd7aa9a0d0d11c7426141c0e","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ba722d061bc4b54802d701fc63fc2fd988934603","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f75fd4b9221d93177c50dcfde671b2e907f53e86","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2022-49540","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}