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Subject: RE:(2) [PATCH 1/4] zstd: pass pointer rathen than structure to
 functions
Reply-To: v.narang@samsung.com
From:   Vaneet Narang <v.narang@samsung.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        "dsterba@suse.cz" <dsterba@suse.cz>
CC:     Maninder Singh <maninder1.s@samsung.com>,
        "herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "keescook@chromium.org" <keescook@chromium.org>,
        "gustavo@embeddedor.com" <gustavo@embeddedor.com>,
        "joe@perches.com" <joe@perches.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        AMIT SAHRAWAT <a.sahrawat@samsung.com>,
        PANKAJ MISHRA <pankaj.m@samsung.com>,
        Vaneet Narang <v.narang@samsung.com>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
        "terrelln@fb.com" <terrelln@fb.com>
In-Reply-To: <20190605143219.248ca514546f69946aa2e07e@linux-foundation.org>
Message-ID: <20190606141019epcms5p1e9c394d2c2ef37506c8004fe48edd29f@epcms5p1>
Date:   Thu, 06 Jun 2019 19:40:19 +0530
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References: <20190605143219.248ca514546f69946aa2e07e@linux-foundation.org>
        <1559552526-4317-1-git-send-email-maninder1.s@samsung.com>
        <1559552526-4317-2-git-send-email-maninder1.s@samsung.com>
        <20190604154326.8868a10f896c148a0ce804d1@linux-foundation.org>
        <20190605115703.GY15290@twin.jikos.cz> <20190605123253.GZ15290@suse.cz>
        <CGME20190603090232epcas5p1630d0584e8a1aa9495edc819605664fc@epcms5p1>
Sender: linux-crypto-owner@vger.kernel.org
Precedence: bulk

Hi Andrew / David,

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=A0=C2=A0ZSTD_parameters=C2=A0params=C2=A0=3D=C2=A0ZSTD_getParams(level,=C2=
=A0src_len,=C2=A00);=0D=0A>>=C2=A0>=C2=A0>=C2=A0+=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0static=C2=A0ZSTD_parameters=C2=A0params;=0D=0A>>=C2=
=A0>=C2=A0=0D=0A>>=C2=A0>=C2=A0>=C2=A0+=0D=0A>>=C2=A0>=C2=A0>=C2=A0+=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0params=C2=A0=3D=C2=A0ZSTD_getPara=
ms(level,=C2=A0src_len,=C2=A00);=0D=0A>>=C2=A0>=C2=A0=0D=0A>>=C2=A0>=C2=A0N=
o=C2=A0thats'=C2=A0broken,=C2=A0the=C2=A0params=C2=A0can't=C2=A0be=C2=A0sta=
tic=C2=A0as=C2=A0it=C2=A0depends=C2=A0on=C2=A0level=C2=A0and=0D=0A>>=C2=A0>=
=C2=A0src_len.=C2=A0What=C2=A0happens=C2=A0if=C2=A0there=C2=A0are=C2=A0seve=
ral=C2=A0requests=C2=A0in=C2=A0parallel=C2=A0with=0D=0A>>=C2=A0>=C2=A0eg.=
=C2=A0different=C2=A0levels?=0D=0A=0D=0AThere=20is=20no=20need=20to=20make=
=20static=20for=20btrfs.=20We=20can=20keep=20it=20as=20a=20stack=20variable=
.=0D=0AThis=20patch=20set=20=20focussed=20on=20reducing=20stack=20usage=20o=
f=20zstd=20compression=20when=20triggered=0D=0Athrough=20zram.=20ZRAM=20int=
ernally=20uses=20crypto=20and=20currently=20crpto=20uses=20fixed=20level=20=
and=20also=0D=0Anot=20dependent=20upon=20source=20length.=0D=0A=0D=0Acrypto=
/zstd.c:=20=20=0D=0Astatic=20ZSTD_parameters=20zstd_params(void)=0D=0A=7B=
=0D=0A=20=20=20=20=20=20=20=20return=20ZSTD_getParams(ZSTD_DEF_LEVEL,=200,=
=200);=0D=0A=7D=0D=0A=0D=0A=0D=0AActually=20high=20stack=20usage=20problem=
=20with=20zstd=20compression=20patch=20gets=20exploited=20more=20incase=20o=
f=20=0D=0Ashrink=20path=20which=20gets=20triggered=20randomly=20from=20any=
=20call=20flow=20in=20case=20of=20low=20memory=20and=20adds=20overhead=0D=
=0Aof=20more=20than=202000=20byte=20of=20stack=20and=20results=20in=20stack=
=20overflow.=0D=0A=0D=0AStack=20usage=20of=20alloc_page=20in=20case=20of=20=
low=20memory=0D=0A=0D=0A=20=20=2072=20=20=20HUF_compressWeights_wksp+0x140/=
0x200=20=20=0D=0A=20=20=2064=20=20=20HUF_writeCTable_wksp+0xdc/0x1c8=20=20=
=20=20=20=20=0D=0A=20=20=2088=20=20=20HUF_compress4X_repeat+0x214/0x450=20=
=20=20=20=20=0D=0A=20=20208=20=20=20ZSTD_compressBlock_internal+0x224/0x137=
c=0D=0A=20=20136=20=20=20ZSTD_compressContinue_internal+0x210/0x3b0=0D=0A=
=20=20192=20=20=20ZSTD_compressCCtx+0x6c/0x144=0D=0A=20=20144=20=20=20zstd_=
compress+0x40/0x58=0D=0A=20=20=2032=20=20=20crypto_compress+0x2c/0x34=0D=0A=
=20=20=2032=20=20=20zcomp_compress+0x3c/0x44=0D=0A=20=20=2080=20=20=20zram_=
bvec_rw+0x2f8/0xa7c=0D=0A=20=20=2064=20=20=20zram_rw_page+0x104/0x170=0D=0A=
=20=20=2048=20=20=20bdev_write_page+0x80/0xb4=0D=0A=20=20112=20=20=20__swap=
_writepage+0x160/0x29c=0D=0A=20=20=2024=20=20=20swap_writepage+0x3c/0x58=0D=
=0A=20=20160=20=20=20shrink_page_list+0x788/0xae0=0D=0A=20=20128=20=20=20sh=
rink_inactive_list+0x210/0x4a8=0D=0A=20=20184=20=20=20shrink_zone+0x53c/0x7=
c0=0D=0A=20=20160=20=20=20try_to_free_pages+0x2fc/0x7cc=0D=0A=20=20=2080=20=
=20=20__alloc_pages_nodemask+0x534/0x91c=0D=0A=0D=0AThanks=20&=20Regards,=
=0D=0AVaneet=20Narang=C2=A0=0D=0A=C2=A0