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Thu, 16 Jan 2020 07:00:59 -0500 Received: from mout.gmx.net ([212.227.15.15]:47235 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726151AbgAPMA5 (ORCPT ); Thu, 16 Jan 2020 07:00:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1579176053; bh=Q+PcaI9rSucZ/tvpFDo2nT6ce1F3hApHl5A6Hs1/qVo=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=DoocIO8Ntx8+uDWM4Mf7599XRs4bHH1FQogKn6/gPGxwJNC8owM3xTT4HqfysIASR xafgpnHNmS2Ac2QHaY+V3BgwoVa31GNyAIHeQfHxZi4mGwPqy+Z7v9ioeuPpkcJy+c mjWbYgC/gRc/CD+/ChdVUdgwUmRgHeCTXA0CXkMo= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.com (mrgmx004 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MrQIv-1jOwj536iF-00oWSS; Thu, 16 Jan 2020 13:00:53 +0100 Subject: Re: [PATCH] Btrfs: always copy scrub arguments back to user space To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <20200116112920.30400-1-fdmanana@kernel.org> From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200116112920.30400-1-fdmanana@kernel.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="grj4DKtEd83EYAPgXAFTD23hTzSMjofzh" X-Provags-ID: V03:K1:g9oY8tvlzWfh2jQkYUMDYKkv/8FyToWpmDRbkihqvSBN0qvMYGX rxVILud0INhYyRbcTh2S/DCZUwYtpEvwOTBX6rvhe7rbyQFaK7xXxkwQ+reNrMNBI4jy7bg XxDKn4/bVOEi8O0lvpx1ybFp9HmumF3TIM7PJiy/U4GLsh+8ze9ITTts8UOuiZvigYKeLfp NBeKDhFNeEfICidU5hGTQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:zIjQyXCTmDI=:lT6IDuXAVDnTXqSTBJE1xR pZvwWi28v2MOc2TSNhLMC8dWIlxachzPLEzcz3xRqsw78NJsnm9Y4ZLmKfNJxziZEgGqR0fv9 BgF6Z8/9mWu6MT0TqG11RQgKn6QQbuKhHTLQZrHqAw5zcQzNVj/dbqEFg3zTPO+wkmAg2L62Q mgFw/OGleB37l4dmgdaVc0gss9gx5ySl7YD9yDrTUw+VkS4QD8lVsquFZB9MyrvmNDawOAtDv 1ktXu/lKXY+m6hhYRGiPcTzsrYtr2yZho0u8S0jgMfpWDUSDKYSdAfX3kGfBNZZf3yQsvP+4l IchPHk13i5uBtRMBgUK3Cp+ksTWpJVDUrFLglG7AFhRGU4/CqWNXD7DTPSJEngtuv+2GSVXC0 EXVEL0472K7beIsYMfjEUcdW84AUesTs/7wJug4p05exuDRDK10ET1FnVNFxrADsMRsQSSHLv bJUmULCg+TmdE6ti9DqLOrJpCcA9ECCFXGNM/i51SKhmiY4JPLZju+YazYp0nMVgXFEcs2tvE SOiGyo01PT6Sev/xaBJK7BCPCEDTX4afDSDY7UqSrEMCQGUc+6m9oDdB38ERg82R1q+fqrUxv S6OELb8nQ5JQP/S62A+fkfbvGEPKqHzAlbHyxlTr7vuCg/v2y4RCwDIy+gKCo/XiN1tX2KBYl LbjTdGeauBqsz22W3bxI9riJyZsUzlIOu504KUTXxuvsHP7zeFb3cowmimnH9G8x9XuVyE+cc YXgVSvEdZA30LEjJP5FdsThIKDFrp+DaDO20+b2Yy0yBA/aqTtomdxOFFV0jzKjt7ie+unnFh VeEDccMZPQHYk+3n0nNDTvHaXIgF+UzycJLXJCya9G8G+GdKW7PS/in7dCSAWYUJD4IzOxPVp T2WG9jzRl9KB4IL/MsHVnHi860eMq4gB1gog77kC7tZi16RnZRtNVYM9QlsL0kDbUytaeaXHE 0/YtH8kd872uilfuMBByaEakOyU33frQPLf1w5BYG7ftUW3omVk7KpY1OexY8QS99IIhlfYR8 yaLVRuK2Zj+tQl95FsNpxXtiNXf3Vz2zY5ZLZVC4BYpUnIwPS13Cq6dDgydjmPJmpD/D6ZgBr SQWKv/tD1GFSJpl5iHqtwSeDo3lnOlXkRGeZ4iZsX0UnOW4J2+X4+AkH+4tZGwe7Lionp1XfF P+/tl02B0xkOro0NlUVBrAZmstTqubEnYTym9kUsZ2MYPTCyWwbnsgYe1/bZYxSKzakI/T5M4 1ELi68XQsR+9xt0/mnBo5wQ0fhCr41S6cu/sxhHSeVpHtYRdVoVsCIyD5Llw= Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --grj4DKtEd83EYAPgXAFTD23hTzSMjofzh Content-Type: multipart/mixed; boundary="P7cUfWo0THEZfMh6Cb5uYzhjMGM1fu7oC" --P7cUfWo0THEZfMh6Cb5uYzhjMGM1fu7oC Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2020/1/16 =E4=B8=8B=E5=8D=887:29, fdmanana@kernel.org wrote: > From: Filipe Manana >=20 > If scrub returns an error we are not copying back the scrub arguments > structure to user space. This prevents user space to know how much prog= ress > scrub has done if an error happened - this includes -ECANCELED which is= > returned when users ask for scrub to stop. A particular use case, which= is > used in btrfs-progs, is to resume scrub after it is canceled, in that c= ase > it relies on checking the progress from the scrub arguments structure a= nd > then use that progress in a call to resume scrub. >=20 > So fix this by always copying the scrub arguments structure to user spa= ce, > overwriting the value returned to user space with -EFAULT only if copyi= ng > the structure failed to let user space know that either that copying di= d > not happen, and therefore the structure is stale, or it happened partia= lly > and the structure is probably not valid and corrupt due to the partial > copy. >=20 > Reported-by: Graham Cobb > Link: https://lore.kernel.org/linux-btrfs/d0a97688-78be-08de-ca7d-bcb4c= 7fb397e@cobb.uk.net/ > Fixes: 06fe39ab15a6a4 ("Btrfs: do not overwrite scrub error with fault = error in scrub ioctl") > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > fs/btrfs/ioctl.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > index 3a4bd5cd67fa..173758d86feb 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -4253,7 +4253,19 @@ static long btrfs_ioctl_scrub(struct file *file,= void __user *arg) > &sa->progress, sa->flags & BTRFS_SCRUB_READONLY, > 0); > =20 > - if (ret =3D=3D 0 && copy_to_user(arg, sa, sizeof(*sa))) > + /* > + * Copy scrub args to user space even if btrfs_scrub_dev() returned a= n > + * error. This is important as it allows user space to know how much > + * progress scrub has done. For example, if scrub is canceled we get > + * -ECANCELED from btrfs_scrub_dev() and return that error back to us= er > + * space. Later user space can inspect the progress from the structur= e > + * btrfs_ioctl_scrub_args and resume scrub from where it left off > + * previously (btrfs-progs does this). > + * If we fail to copy the btrfs_ioctl_scrub_args structure to user sp= ace > + * then return -EFAULT to signal the structure was not copied or it m= ay > + * be corrupt and unreliable due to a partial copy. > + */ > + if (copy_to_user(arg, sa, sizeof(*sa))) > ret =3D -EFAULT; > =20 > if (!(sa->flags & BTRFS_SCRUB_READONLY)) >=20 --P7cUfWo0THEZfMh6Cb5uYzhjMGM1fu7oC-- --grj4DKtEd83EYAPgXAFTD23hTzSMjofzh Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAl4gUHEACgkQwj2R86El /qhKjAf/QH2rQD2SYdQAKNdZgGcMsqMcj47QRn1RjTdqXWpFHNmPVAePxb1IJLyt D9LRTkBRSH3B2MrlgnDyNDjJCeXYIydy3UC5xsKWZGZ0xHLevMjzOCgCxicPYAtu vPnDSyg74tz7WaOgX70d9V/sa8cvWR9x4zBhLKgPYtmC805VlT+hHqxzkQfgORr2 /miQt5rmW2dzzUEt1ziajRapN4modY9xX4L6tpmp2mjGxOEcxepuzghOP+2D0ZqR cgtxw8ds0xCNhSnTsarKIM31EALErQ/HKSaEanwxNwxj9fN1FTP5NB6XJReCbWfi VD7doxVQhcn8ymJj77J6uubqM7UHZw== =iOJC -----END PGP SIGNATURE----- --grj4DKtEd83EYAPgXAFTD23hTzSMjofzh--