Date: Sun, 12 Jul 2020 15:06:49 -0700 From: Xin Li <delphij@delphij.net> To: freebsd-current@freebsd.org Subject: Re: Is there any error checking on swap? Message-ID: <a5b48324-c02c-b087-7da4-be66e447599f@delphij.net> In-Reply-To: <20200712072911.GG4213@funkthat.com> References: <20200712033332.GA63411@www.zefox.net> <20200712072911.GG4213@funkthat.com>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --LMnbsEF8WeMUkozyo6orSrKHBIwGgugr0 Content-Type: multipart/mixed; boundary="UGCJhs9mWmeFod3EV4IksQZz4eH5wRmpc"; protected-headers="v1" From: Xin Li <delphij@delphij.net> Reply-To: d@delphij.net To: freebsd-current@freebsd.org Message-ID: <a5b48324-c02c-b087-7da4-be66e447599f@delphij.net> Subject: Re: Is there any error checking on swap? References: <20200712033332.GA63411@www.zefox.net> <20200712072911.GG4213@funkthat.com> In-Reply-To: <20200712072911.GG4213@funkthat.com> --UGCJhs9mWmeFod3EV4IksQZz4eH5wRmpc Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 7/12/20 12:29 AM, John-Mark Gurney wrote: > bob prohaska wrote this message on Sat, Jul 11, 2020 at 20:33 -0700: >> Is there any error checking on swap traffic, along the lines of >> a checksum or parity test?=20 >> >> Just curious what happens if a page written out is corrupted when >> it comes back. >=20 > Looks like it doesn't: > https://svnweb.freebsd.org/base/head/sys/vm/swap_pager.c?annotate=3D361= 965#l1389 Technically one can enable checks with e.g. geli(8), but note that the geli(8) provider will not "prime" the HMAC data so attaching the device will immediately spam the system log with some authentication errors due to GEOM tasting (because the kernel would try to read locations that potentially contain metadata for other GEOM providers). For the case of swap, since the write is always page sized, it's probably optimal to implement something in the swap layer itself and store the expected checksums in memory. Cheers, --UGCJhs9mWmeFod3EV4IksQZz4eH5wRmpc-- --LMnbsEF8WeMUkozyo6orSrKHBIwGgugr0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.2.20 (FreeBSD) iQIzBAEBCgAdFiEEceNg5NEMZIki80nQQHl/fJX0g08FAl8LiX0ACgkQQHl/fJX0 g09xQQ//UXdeg1WXxoi0WQR8Dr1xwLeKUhW+KULfN3wuH0M8feIcVZca033Ra8w4 rMdx9HF7H87vbgUb4Cw1UfcAyLgJSbQ09tV0m3O6NRgI9E9Awfys0vVIOnpvrcI7 R1VTHqYqiI2iKuaxf0aY/YVoMQWXGeP7G45dKUk/jhXC9XfSphhep0xUOacm7cyp W14uIn8mDeEyHCjEByxfuZ3Xefg8cO7hwcgDCRY3qK+Wd3D1hOwRvQkPSbzTyLJA QITqqZFnGbiTTpSO+IIkmFdH+HfvM7R6lZOuNAC7PG0+0neosCG82wRwH2XTzRhz g49dWL+NXheTJhaTQ5CStMZw3dnNafm9nuxLkA2OtHuRsVYmJUHXj9ynRAVJd8dA A/G/6Dk9mtkZW+cIEft0jqmF9iVdv/pPH/efyJaJtarabr8rZztefn8vbZ5P6pKW nAZLcSBdGo1AhVaGEaK9dneQ1mFn7DFsQBjv1gGYPR3TKXXC4GfbZWTLlapiAZ8U BaIYtk6YgR819w21Qk0OBNh+zTLuAxTpwMJo02xOTgPRbIZ9b5hzR+c7MlIULlvY 6mBiB4omc5lqvWRC+8QR/kFXTMxkrghA405uiBwX+z9s8EEdJuOaNm948GqGxW7N Hn4PNyUFyILqiRUGTlUL3jSPq4O3jLl7L+wJ+Y6XFx32qrN8RC8= =cW4G -----END PGP SIGNATURE----- --LMnbsEF8WeMUkozyo6orSrKHBIwGgugr0--
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