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SubjectRe: [PATCH v2] Uprobes: Fix kernel oops with delayed_uprobe_remove()
* Ravi Bangoria <ravi.bangoria@linux.ibm.com> [2018-12-05 09:04:23]:

> There could be a race between task exit and probe unregister:
>
> exit_mm()
> mmput()
> __mmput() uprobe_unregister()
> uprobe_clear_state() put_uprobe()
> delayed_uprobe_remove() delayed_uprobe_remove()
>
> put_uprobe() is calling delayed_uprobe_remove() without taking
> delayed_uprobe_lock and thus the race sometimes results in a
> kernel crash. Fix this by taking delayed_uprobe_lock before
> calling delayed_uprobe_remove() from put_uprobe().
>
> Detailed crash log can be found at:
> https://lkml.org/lkml/2018/11/1/1244
>
> Reported-by: syzbot+cb1fb754b771caca0a88@syzkaller.appspotmail.com
> Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)")
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>

Looks good to me.

Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> kernel/events/uprobes.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 322e97bbb437..abbd8da9ac21 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -572,7 +572,9 @@ static void put_uprobe(struct uprobe *uprobe)
> * gets called, we don't get a chance to remove uprobe from
> * delayed_uprobe_list from remove_breakpoint(). Do it here.
> */
> + mutex_lock(&delayed_uprobe_lock);
> delayed_uprobe_remove(uprobe, NULL);
> + mutex_unlock(&delayed_uprobe_lock);
> kfree(uprobe);
> }
> }
> --
> 2.19.2
>

--
Thanks and Regards
Srikar Dronamraju

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