linux-kernel - Re: [PATCH v3 1/1] pgo: Fix sleep in atomic section in prf

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Date:   Tue, 08 Jun 2021 16:50:45 +0300
From:   jarmo.tiitto@...il.com
To:     Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        clang-built-linux@...glegroups.com, Bill Wendling <wcw@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org
Cc:     morbo@...gle.com, Jarmo Tiitto <jarmo.tiitto@...il.com>
Subject: Re: [PATCH v3 1/1] pgo: Fix sleep in atomic section in prf_open() v3

Kees Cook wrote tiistaina 8. kesäkuuta 2021 2.02.51 EEST:
> On Sat, 5 Jun 2021 21:31:29 +0300, Jarmo Tiitto wrote:
> > In prf_open() the required buffer size can be so large that
> > vzalloc() may sleep thus triggering bug:
> > 
> > ======
> > 
> >  BUG: sleeping function called from invalid context at
> >  include/linux/sched/mm.h:201 in_atomic(): 1, irqs_disabled(): 1,
> >  non_block: 0, pid: 337, name: cat CPU: 1 PID: 337 Comm: cat Not tainted
> >  5.13.0-rc2-24-hack+ #154
> >  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> >  
> >  Call Trace:
> >   dump_stack+0xc7/0x134
> >   ___might_sleep+0x177/0x190
> >   __might_sleep+0x5a/0x90
> >   kmem_cache_alloc_node_trace+0x6b/0x3a0
> >   ? __get_vm_area_node+0xcd/0x1b0
> >   ? dput+0x283/0x300
> >   __get_vm_area_node+0xcd/0x1b0
> >   __vmalloc_node_range+0x7b/0x420
> >   ? prf_open+0x1da/0x580
> >   ? prf_open+0x32/0x580
> >   ? __llvm_profile_instrument_memop+0x36/0x50
> >   vzalloc+0x54/0x60
> >   ? prf_open+0x1da/0x580
> >   prf_open+0x1da/0x580
> >   full_proxy_open+0x211/0x370
> >   ....
> > 
> > ======
> > 
> > [...]
> 
> Applied to for-next/clang/features, thanks! I made some additional tweaks
> on top of this, in a separate patch I just sent out.
> 
> [1/1] pgo: Fix sleep in atomic section in prf_open() v3
>       https://git.kernel.org/kees/c/d13b0485a7bb
> 
> --
> Kees Cook

Oof. Looking now at your fixes, I'm sorry for the extra work needed. :-|
I should have cleaned up the error paths better, since that was mentioned 
earlier.
My eyes were apparently pointed on the v2 module profiling code I have been 
brewing the past weekend. 

Thanks!
--
Jarmo