linux-kernel - Re: Avoid VLA in pgd_alloc kills boot on 32-bit machines was Re: -next20181010,1011 regression: thinkpad x60 (32 bit) dies during boot.

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Message-ID: <20181012182233.GB9098@amd>
Date:   Fri, 12 Oct 2018 20:22:33 +0200
From:   Pavel Machek <pavel@....cz>
To:     Ingo Molnar <mingo@...nel.org>, arnd@...db.de,
        akpm@...ux-foundation.org, luto@...nel.org,
        dave.hansen@...ux.intel.com, jroedel@...e.de,
        keescook@...omium.org, torvalds@...ux-foundation.org,
        toshi.kani@....com
Cc:     Thomas Gleixner <tglx@...utronix.de>, sfr@...b.auug.org.au,
        kernel list <linux-kernel@...r.kernel.org>, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org
Subject: Re: Avoid VLA in pgd_alloc kills boot on 32-bit machines was Re:
 -next20181010,1011 regression: thinkpad x60 (32 bit) dies during boot.

On Fri 2018-10-12 20:10:11, Pavel Machek wrote:
> Hi!
> 
> > > > So what came in between -next20181005 and the first bad one? kernel/sched/*
> > > > being the first place to look at.
> > > 
> > > kernel/sched does not seem to contain anything too scary.
> > > 
> > > I know that -next20181005 works ok, and I know -next20181010 is
> > > bad. Is there easy way to bisect using that information? I can do
> > > bisect between -next and mainline, but that's a lot of patches and
> > > thus not much fun :-(.
> > > 
> > > In the meantime, I reproduced the failure with T40p. Is there someone
> > > with working x86-32 in -next?
> > 
> > Does latest -tip fail too? If yes then I suspect bisection would be needed.
> 
> And the winner is...
> 
> [1be3f247c2882a82279cbcf43717581ea943b692] x86/mm: Avoid VLA in
> pgd_alloc()
> 
> "Kernel stack is corrupted in: pgd_alloc" panic kind of suggests this
> is right commit.

git bisect log, for the reference... and ~ my config.

									Pavel

# bad: [771b65e89c8a51d611b8049718693a4202e4f732] Add linux-next specific files for 20181011
# good: [7876320f88802b22d4e2daf7eb027dd14175a0f8] Linux 4.19-rc4
git bisect start '771b65e89c8a51d611b8049718693a4202e4f732' '7876320f88802b22d4e2daf7eb027dd14175a0f8'
# good: [43faff25da004eabce691268da34065b3690f5ca] Merge remote-tracking branch 'net-next/master'
git bisect good 43faff25da004eabce691268da34065b3690f5ca
# good: [3e2beb7db82a880319aa2f0dcafa820f3f5206d3] Merge remote-tracking branch 'spi/for-next'
git bisect good 3e2beb7db82a880319aa2f0dcafa820f3f5206d3
# bad: [74411e5fd30ae540491c4d6142af6ee6b2b22f09] Merge remote-tracking branch 'char-misc/char-misc-next'
git bisect bad 74411e5fd30ae540491c4d6142af6ee6b2b22f09
# bad: [c810d907775aa2aa753e836a122613fd2416b14d] Merge remote-tracking branch 'kvm/linux-next'
git bisect bad c810d907775aa2aa753e836a122613fd2416b14d
# good: [fac07d2ba7b2764e3002ff9bc7861742a84a2ef6] Merge branch 'perf/core'
git bisect good fac07d2ba7b2764e3002ff9bc7861742a84a2ef6
# bad: [d74865bd3996c7a6f3e8ce6e626c1fe474e39494] Merge branch 'x86/mm'
git bisect bad d74865bd3996c7a6f3e8ce6e626c1fe474e39494
# good: [dcd2d0cece1608b2be9184786c900807ec947076] Merge branch 'x86/asm'
git bisect good dcd2d0cece1608b2be9184786c900807ec947076
# bad: [ae9260d80e517c8702b91b8e00d117e1e2834c33] Merge branch 'x86/cache'
git bisect bad ae9260d80e517c8702b91b8e00d117e1e2834c33
# good: [d5a581d84ae6b8a4a740464b80d8d9cf1e7947b2] x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs
git bisect good d5a581d84ae6b8a4a740464b80d8d9cf1e7947b2
# good: [245e5707dd7df01428459d97a9121f14a57dac6b] Merge branch 'x86/build'
git bisect good 245e5707dd7df01428459d97a9121f14a57dac6b
# bad: [7d27cb68cc307ee103e116d357e9baca35151c55] Merge branch 'x86/urgent' into x86/cache
git bisect bad 7d27cb68cc307ee103e116d357e9baca35151c55
# good: [2cc81c6992248ea37d0241bc325977bab310bc3b] x86/intel_rdt: Show missing resctrl mount options
git bisect good 2cc81c6992248ea37d0241bc325977bab310bc3b
# bad: [e8bd1803aec89dfce5758d88022963fe3248bc4c] x86/intel_rdt: Fix out-of-bounds memory access in CBM tests
git bisect bad e8bd1803aec89dfce5758d88022963fe3248bc4c


-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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