DEBIAN-CVE-2022-49540

In the Linux kernel, the following vulnerability has been resolved: rcu-tasks: Fix race in schedule and flush work While booting secondary CPUs, cpusread[lock/unlock] is not keeping online cpumask stable. The transient online mask results in below calltrace. [ 0.324121] CPU1: Booted secondary processor 0x0000000001 [0x410fd083] [ 0.346652] Detected PIPT I-cache on CPU2 [ 0.347212] CPU2: Booted secondary processor 0x0000000002 [0x410fd083] [ 0.377255] Detected PIPT I-cache on CPU3 [ 0.377823] CPU3: Booted secondary processor 0x0000000003 [0x410fd083] [ 0.379040] ------------[ cut here ]------------ [ 0.383662] WARNING: CPU: 0 PID: 10 at kernel/workqueue.c:3084 __flushwork+0x12c/0x138 [ 0.384850] Modules linked in: [ 0.385403] CPU: 0 PID: 10 Comm: rcutasksrude Not tainted 5.17.0-rc3-v8+ #13 [ 0.386473] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT) [ 0.387289] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 0.388308] pc : __flush_work+0x12c/0x138 [ 0.388970] lr : __flush_work+0x80/0x138 [ 0.389620] sp : ffffffc00aaf3c60 [ 0.390139] x29: ffffffc00aaf3d20 x28: ffffffc009c16af0 x27: ffffff80f761df48 [ 0.391316] x26: 0000000000000004 x25: 0000000000000003 x24: 0000000000000100 [ 0.392493] x23: ffffffffffffffff x22: ffffffc009c16b10 x21: ffffffc009c16b28 [ 0.393668] x20: ffffffc009e53861 x19: ffffff80f77fbf40 x18: 00000000d744fcc9 [ 0.394842] x17: 000000000000000b x16: 00000000000001c2 x15: ffffffc009e57550 [ 0.396016] x14: 0000000000000000 x13: ffffffffffffffff x12: 0000000100000000 [ 0.397190] x11: 0000000000000462 x10: ffffff8040258008 x9 : 0000000100000000 [ 0.398364] x8 : 0000000000000000 x7 : ffffffc0093c8bf4 x6 : 0000000000000000 [ 0.399538] x5 : 0000000000000000 x4 : ffffffc00a976e40 x3 : ffffffc00810444c [ 0.400711] x2 : 0000000000000004 x1 : 0000000000000000 x0 : 0000000000000000 [ 0.401886] Call trace: [ 0.402309] _flushwork+0x12c/0x138 [ 0.402941] scheduleoneachcpu+0x228/0x278 [ 0.403693] rcutasksrudewaitgp+0x130/0x144 [ 0.404502] rcutaskskthread+0x220/0x254 [ 0.405264] kthread+0x174/0x1ac [ 0.405837] retfromfork+0x10/0x20 [ 0.406456] irq event stamp: 102 [ 0.406966] hardirqs last enabled at (101): [<ffffffc0093c8468>] rawspinunlockirq+0x78/0xb4 [ 0.408304] hardirqs last disabled at (102): [<ffffffc0093b8270>] el1dbg+0x24/0x5c [ 0.409410] softirqs last enabled at (54): [<ffffffc0081b80c8>] localbhenable+0xc/0x2c [ 0.410645] softirqs last disabled at (50): [<ffffffc0081b809c>] localbhdisable+0xc/0x2c [ 0.411890] ---[ end trace 0000000000000000 ]--- [ 0.413000] smp: Brought up 1 node, 4 CPUs [ 0.413762] SMP: Total of 4 processors activated. [ 0.414566] CPU features: detected: 32-bit EL0 Support [ 0.415414] CPU features: detected: 32-bit EL1 Support [ 0.416278] CPU features: detected: CRC32 instructions [ 0.447021] Callback from callrcutasksrude() invoked. [ 0.506693] Callback from callrcutasks() invoked. This commit therefore fixes this issue by applying a single-CPU optimization to the RCU Tasks Rude grace-period process. The key point here is that the purpose of this RCU flavor is to force a schedule on each online CPU since some past event. But the rcutasksrudewaitgp() function runs in the context of the RCU Tasks Rude's grace-period kthread, so there must already have been a context switch on the current CPU since the call to either synchronizercutasksrude() or callrcutasksrude(). So if there is only a single CPU online, RCU Tasks Rude's grace-period kthread does not need to anything at all. It turns out that the rcutasksrudewaitgp() function's call to scheduleoneachcpu() causes problems during early boot. During that time, there is only one online CPU, namely the boot CPU. Therefore, applying this single-CPU optimization fixes early-boot instances of this problem.