linux-kernel - Re: [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:   Tue, 22 Oct 2019 09:43:54 -0400 (EDT)
From:   Dave Anderson <anderson@...hat.com>
To:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3 v4] x86/kdump: always reserve the low 1MiB when the
 crashkernel option is specified


---- Original Message -----

> > 
> > [root linux]$ crash vmlinux
> > /var/crash/127.0.0.1-2019-09-19-08\:31\:27/vmcore
> > WARNING: kernel relocated [240MB]: patching 97110 gdb minimal_symbol values
> > 
> >       KERNEL: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmlinux
> >     DUMPFILE: /var/crash/127.0.0.1-2019-09-19-08:31:27/vmcore  [PARTIAL DUMP]
> >         CPUS: 128
> >         DATE: Thu Sep 19 08:31:18 2019
> >       UPTIME: 00:01:21
> > LOAD AVERAGE: 0.16, 0.07, 0.02
> >        TASKS: 1343
> >     NODENAME: amd-ethanol
> >      RELEASE: 5.3.0-rc7+
> >      VERSION: #4 SMP Thu Sep 19 08:14:00 EDT 2019
> >      MACHINE: x86_64  (2195 Mhz)
> >       MEMORY: 127.9 GB
> >        PANIC: "Kernel panic - not syncing: sysrq triggered crash"
> >          PID: 9789
> >      COMMAND: "bash"
> >         TASK: "ffff89711894ae80  [THREAD_INFO: ffff89711894ae80]"
> >          CPU: 83
> >        STATE: TASK_RUNNING (PANIC)
> > 
> > crash> kmem -s|grep -i invalid
> > kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4
> > kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4
> > crash>
> 
> I fail to see what that's trying to tell me? You have invalid pointers?

Correct, because the pointer values are encrypted.  The command is walking through the
singly-linked list of free objects in a slab from the dma-kmalloc-512 slab cache.  The
slab memory had been allocated from low memory, and because of the  problem at hand,
it was was copied to the vmcore in its encrypted state.

Dave