On Mon, Feb 27, 2023 at 11:49 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > Hey Steve, > > On Mon, Feb 27, 2023 at 10:33 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > On Mon, 27 Feb 2023 08:15:26 -0500 > > Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > > >> asm_sysvec_apic_timer_interrupt+0x1a/0x20 > > > >> RIP: 0010:default_idle+0xf/0x20 > > > >> Code: 89 07 49 c7 c0 08 00 00 00 4d 29 c8 4c 01 c7 4c 29 c2 e9 76 ff ff ff cc cc cc cc f3 0f 1e fa eb 07 0f 00 2d e3 8a 34 00 fb f4 <fa> c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 65 > > > >> RSP: 0018:ffffc9000017fe00 EFLAGS: 00000202 > > > >> RAX: 0000000000dfbea1 RBX: dffffc0000000000 RCX: ffffffff89b1da9c > > > >> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 > > > >> RBP: 0000000000000007 R08: 0000000000000001 R09: ffff888119fb6c23 > > > >> R10: ffffed10233f6d84 R11: dffffc0000000000 R12: 0000000000000003 > > > >> R13: ffff888100833900 R14: ffffffff8e112850 R15: 0000000000000000 > > > >> default_idle_call+0x67/0xa0 > > > >> do_idle+0x361/0x440 > > > >> cpu_startup_entry+0x18/0x20 > > > >> start_secondary+0x256/0x300 > > > >> secondary_startup_64_no_verify+0xce/0xdb > > > >> </TASK> > > > >> Modules linked in: > > > >> CR2: 0000000000000000 > > > >> ---[ end trace 0000000000000000 ]--- > > > >> RIP: 0010:0x0 > > > >> Code: Unable to access opcode bytes at 0xffffffffffffffd6. > > > > > > I have seen this exact signature when the processor tries to execute a function that has a NULL address. That causes IP to goto 0 and the exception. Sounds like something corrupted rcu_head (Just a guess). > > > > [ Joel, you need to line wrap your emails ;-) ] > > Ok I will try. The thing is, I have not figured out yet how to > plaintext-reply from my iPhone without having it wrap :-( > > > This looks like a call_rcu() was called on something that later got freed > > or reused. That is, the bug is not with RCU but with something using RCU. > > Yes certainly, the rcu_head is allocated on the caller side so it > could have been trampled while the callback was still in flight. Thank you all for your guidance, I learned a lot during this process > > > OR it could be a bug with RCU if the synchronize_rcu() ended before the > > grace periods have finished. Thanks again. By the way, the syzkaller on my local machine has been running for 8 hours, only three bugs reported[1][2][3], but they don't seem to be related to Sanan's original report. Maybe there are some configuration mismatches between us.The test continues, I will report to you once I have any new discovery. [1] http://154.220.3.120:56700/ [2] https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/next/linux-next.git/snapshot/linux-next-next-20230221.tar.gz [3] http://154.220.3.120/configs/linux-next-config-20230221.txt Thanks Zhouyi > > Good point.. > > Thanks, > > - Joel
