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From: Mukesh Ojha <>
To: <>
Cc: <>, <>,
	<>, <>,
	"Rafael J. Wysocki" <>
Subject: Possible race in dev_coredumpm()-del_timer() path
Date: Wed, 13 Apr 2022 10:59:22 +0530	[thread overview]
Message-ID: <> (raw)

Hi All,

We are hitting one race due to which try_to_grab_pending() is stuck .
In following scenario, while running (p1)dev_coredumpm() devcd device is 
added to
the framework and uevent notification sent to userspace that result in 
the call to (p2) devcd_data_write()
which eventually try to delete the queued timer which in the racy 
scenario timer is not queued yet.
So, debug object report some warning and in the meantime timer is 
initialized and queued from p1 path.
and from p2 path it gets overriden again timer->entry.pprev=NULL and 
try_to_grab_pending() stuck
as del_timer() always return 0 as timer_pending() return false.

P1 P2(X)


                                           Uevent notification sent to 
                                           for device addition

             device_add() ========================>                 
Process X reads this uevents
notification and do write call
that results in call to


                    (&devcd->del_wk, devcd_del);

do_init_timer()   ==> reinitialized the timer to timer->entry.pprev=NULL



             reply	other threads:[~2022-04-13  5:29 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-13  5:29 Mukesh Ojha [this message]
2022-04-13  5:34 ` Possible race in dev_coredumpm()-del_timer() path Greg KH
2022-04-13  6:41   ` Johannes Berg
2022-04-13 10:16   ` Mukesh Ojha
2022-04-13 10:58     ` Greg KH
2022-04-13 11:21       ` Mukesh Ojha
2022-04-13 13:01         ` Greg KH
2022-04-13 14:17       ` Mukesh Ojha
2022-04-13 14:18       ` Mukesh Ojha
2022-04-14 10:38       ` Thomas Gleixner
2022-04-14 11:20         ` Mukesh Ojha
2022-04-14 11:31           ` Thomas Gleixner

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