lkml.org 
[lkml]   [2021]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] tpm: Fix crash on tmprm release
On Tue, Jun 15, 2021 at 03:18:48PM +0200, Jarkko Sakkinen wrote:
> On Tue, Jun 15, 2021 at 11:14:09AM +0200, Vincent Whitchurch wrote:
> > If the tpm_tis module is removed (or a system shutdown is triggered)
> > while the tpmrm device is use, the kernel crashes due to chip->ops being
> > NULL:
> >
> > # exec 3<>/dev/tpmrm0
> > # rmmod tpm_tis
> > # exit
> > ==================================================================
> > BUG: KASAN: null-ptr-deref in tpm_chip_start+0x2d/0x120 [tpm]
> > Read of size 8 at addr 0000000000000060 by task sh/994
> >
> > Call Trace:
> > kasan_report.cold.13+0x10f/0x111
> > tpm_chip_start+0x2d/0x120 [tpm]
> > tpm2_del_space+0x2c/0xa0 [tpm]
> > tpmrm_release+0x3f/0x50 [tpm]
> > __fput+0x110/0x3c0
> > task_work_run+0x94/0xd0
> > do_exit+0x683/0x13e0
> > do_group_exit+0x8b/0x140
> > do_syscall_64+0x3c/0x80
> > ==================================================================
> >
> > Fix this by making tpm2_del_space() use tpm_try_get_ops(). The latter
> > already includes the calls to tpm_chip_start() and tpm_chip_stop().
>
> This lacks explanation why migrating to tpm_try_get_ops() fixes the
> issue. Saying that doing something fixes something is not good enough
> explanation. So, can you extend this paragraph just a bit in the next
> version?

Thank you for the review, but I see now that James already proposed a
more-or-less identical fix earlier, so I'll let that patch run its due
course:

https://lore.kernel.org/linux-integrity/e7566e1e48f5be9dca034b4bfb67683b5d3cb88f.camel@HansenPartnership.com/
https://lore.kernel.org/linux-integrity/327f4c87-e652-6cbe-c624-16a6edf0c31d@kunbus.com/

\
 
 \ /
  Last update: 2021-06-17 07:45    [W:0.066 / U:0.164 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site