On Fri, Oct 27, 2017 at 02:33:48PM +0200, Borislav Petkov wrote: > On Fri, Oct 27, 2017 at 07:42:45PM +0800, zhouchengming wrote: > > This is a real bug happened on one of our machines, below is the calltrace. > > We can see the trigger is at alternatives_text_reserved+0x20/0x80, and > > encounter a deleted (poisoned) list_head. > > Looks like some out-of-tree, old kernel thing. We don't have > mlx4_stats_sysfs_create() upstream and looking at the boot timestamps, > it could be that register_jprobe() is not ready yet. > > Looking at the Code, though: > > 20: 74 59 je 0x7b > 22: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1) > 29: 00 00 > 2b:* 48 3b 71 20 cmp 0x20(%rcx),%rsi <-- trapping > instruction > 2f: 72 3a jb 0x6b > 31: 48 3b 79 28 cmp 0x28(%rcx),%rdi > 35: 77 34 ja 0x6b > > %rcx is 0xdead0000000000d0 and that is POISON_POINTER_DELTA + 0xd0 so > that looks more like smp_alt_modules is not initialized yet but I could > could very well be wrong because this is an old kernel. So trigger that > with the upstream kernel without out of tree modules.
Not to mention that we're about (or just have) yanked jprobes out of the kernel entirely.
