linux-kernel - Re: [RT BUG] Mismatched get_uid/free_uid usage in signals in some rts (2nd try)

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Date:   Fri, 24 Jun 2022 09:58:07 -0700
From:   Mark Gross <markgross@...nel.org>
To:     Joe Korty <Joe.Korty@...current-rt.com>
Cc:     Mark Gross <markgross@...nel.org>,
        "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux RT users <linux-rt-users@...hiver.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RT BUG] Mismatched get_uid/free_uid usage in signals in some
 rts (2nd try)

On Tue, Jun 21, 2022 at 03:16:39PM +0000, Joe Korty wrote:
> Mismatched get_uid/free_uid usage in signals in 4.9.312-rt193
> 
>      [  First attempt using mutt did not show up on the mailing lists.
>         Trying again with office365 Outlook.   Also added the 4.9-rt
>         maintainers. ]
> 
> The 4.19-rt patch,
> 
>    0329-signal-Prevent-double-free-of-user-struct.patch
> 
> needs to be ported to LAG 4.9-rt, as that release now has the Linus commit,
What does LAG stand for?

FWIW the cherry-pick within the RT-stable tree worked without conflict.
    (cherry picked from commit a99e09659e6cd4b633c3689f2c3aa5f8a816fe5b)
It compiles.
See 58a584ee59b2 signal: Prevent double-free of user struct in 
linux-stable-rt.git/v4.9-rt-next

> 
>    fda31c50292a ("signal: avoid double atomic counter increments for user accounting")
>
This was added to 4.9.y on March 20, 2020.
commit 4306259ff6b8b682322d9aeb0c12b27c61c4a548 in linux-stable.

How did you find this issue?  What is missing from my testing?

Do you have a test case that I can conferm my cherry-pick works?
Could you test the v4.9-rt-next branch to see if it fixes you issue?

--mark

> which breaks the longstanding rt patch,
> 
>    0259-signals-Allow-rt-tasks-to-cache-one-sigqueue-struct.patch
> 
> Current application status:
> 
>    4.4.302-rt232        OK      has both Linus's patch and the fix needed for rt.
>    4.9.312-rt193        BROKE   has Linus's patch but not the fix.
>    4.14.87-rt50         OK      does NOT have either Linus's patch nor its rt fix.
>    4.19.246-rt110       OK      has both Linus's patch and the fix needed for rt.
>    5.4.193-rt74         OK	has both Linus's patch and the fix needed for rt.
>    5.10.120-rt70        OK	has both Linus's patch and the fix needed for rt.
>    5.15.44-rt46         UNKNOWN no get_uid/free_uid usage in kernel/signal.c anymore.
> 
> Regards,
> Joe