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Wed, 13 Nov 2019 14:06:04 -0500 Received: from 1.general.cking.uk.vpn ([10.172.193.212]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iUxwa-0000xi-Sg; Wed, 13 Nov 2019 19:04:44 +0000 Subject: Re: [PATCH][V3] ovl: fix lookup failure on multi lower squashfs To: Amir Goldstein Cc: Miklos Szeredi , overlayfs , linux-kernel References: <20191113175746.110933-1-colin.king@canonical.com> From: Colin Ian King Autocrypt: addr=colin.king@canonical.com; prefer-encrypt=mutual; keydata= mQINBE6TJCgBEACo6nMNvy06zNKj5tiwDsXXS+LhT+LwtEsy9EnraKYXAf2xwazcICSjX06e fanlyhB0figzQO0n/tP7BcfMVNG7n1+DC71mSyRK1ZERcG1523ajvdZOxbBCTvTitYOy3bjs +LXKqeVMhK3mRvdTjjmVpWnWqJ1LL+Hn12ysDVVfkbtuIm2NoaSEC8Ae8LSSyCMecd22d9Pn LR4UeFgrWEkQsqROq6ZDJT9pBLGe1ZS0pVGhkRyBP9GP65oPev39SmfAx9R92SYJygCy0pPv BMWKvEZS/7bpetPNx6l2xu9UvwoeEbpzUvH26PHO3DDAv0ynJugPCoxlGPVf3zcfGQxy3oty dNTWkP6Wh3Q85m+AlifgKZudjZLrO6c+fAw/jFu1UMjNuyhgShtFU7NvEzL3RqzFf9O1qM2m uj83IeFQ1FZ65QAiCdTa3npz1vHc7N4uEQBUxyXgXfCI+A5yDnjHwzU0Y3RYS52TA3nfa08y LGPLTf5wyAREkFYou20vh5vRvPASoXx6auVf1MuxokDShVhxLpryBnlKCobs4voxN54BUO7m zuERXN8kadsxGFzItAyfKYzEiJrpUB1yhm78AecDyiPlMjl99xXk0zs9lcKriaByVUv/NsyJ FQj/kmdxox3XHi9K29kopFszm1tFiDwCFr/xumbZcMY17Yi2bQARAQABtCVDb2xpbiBLaW5n IDxjb2xpbi5raW5nQGNhbm9uaWNhbC5jb20+iQI2BBMBCAAhBQJOkyQoAhsDBQsJCAcDBRUK CQgLBRYCAwEAAh4BAheAAAoJEGjCh9/GqAImsBcP9i6C/qLewfi7iVcOwqF9avfGzOPf7CVr n8CayQnlWQPchmGKk6W2qgnWI2YLIkADh53TS0VeSQ7Tetj8f1gV75eP0Sr/oT/9ovn38QZ2 vN8hpZp0GxOUrzkvvPjpH+zdmKSaUsHGp8idfPpZX7XeBO0yojAs669+3BrnBcU5wW45SjSV nfmVj1ZZj3/yBunb+hgNH1QRcm8ZPICpjvSsGFClTdB4xu2AR28eMiL/TTg9k8Gt72mOvhf0 fS0/BUwcP8qp1TdgOFyiYpI8CGyzbfwwuGANPSupGaqtIRVf+/KaOdYUM3dx/wFozZb93Kws gXR4z6tyvYCkEg3x0Xl9BoUUyn9Jp5e6FOph2t7TgUvv9dgQOsZ+V9jFJplMhN1HPhuSnkvP 5/PrX8hNOIYuT/o1AC7K5KXQmr6hkkxasjx16PnCPLpbCF5pFwcXc907eQ4+b/42k+7E3fDA Erm9blEPINtt2yG2UeqEkL+qoebjFJxY9d4r8PFbEUWMT+t3+dmhr/62NfZxrB0nTHxDVIia u8xM+23iDRsymnI1w0R78yaa0Eea3+f79QsoRW27Kvu191cU7QdW1eZm05wO8QUvdFagVVdW Zg2DE63Fiin1AkGpaeZG9Dw8HL3pJAJiDe0KOpuq9lndHoGHs3MSa3iyQqpQKzxM6sBXWGfk EkK5Ag0ETpMkKAEQAMX6HP5zSoXRHnwPCIzwz8+inMW7mJ60GmXSNTOCVoqExkopbuUCvinN 4Tg+AnhnBB3R1KTHreFGoz3rcV7fmJeut6CWnBnGBtsaW5Emmh6gZbO5SlcTpl7QDacgIUuT v1pgewVHCcrKiX0zQDJkcK8FeLUcB2PXuJd6sJg39kgsPlI7R0OJCXnvT/VGnd3XPSXXoO4K cr5fcjsZPxn0HdYCvooJGI/Qau+imPHCSPhnX3WY/9q5/WqlY9cQA8tUC+7mgzt2VMjFft1h rp/CVybW6htm+a1d4MS4cndORsWBEetnC6HnQYwuC4bVCOEg9eXMTv88FCzOHnMbE+PxxHzW 3Gzor/QYZGcis+EIiU6hNTwv4F6fFkXfW6611JwfDUQCAHoCxF3B13xr0BH5d2EcbNB6XyQb IGngwDvnTyKHQv34wE+4KtKxxyPBX36Z+xOzOttmiwiFWkFp4c2tQymHAV70dsZTBB5Lq06v 6nJs601Qd6InlpTc2mjd5mRZUZ48/Y7i+vyuNVDXFkwhYDXzFRotO9VJqtXv8iqMtvS4xPPo 2DtJx6qOyDE7gnfmk84IbyDLzlOZ3k0p7jorXEaw0bbPN9dDpw2Sh9TJAUZVssK119DJZXv5 2BSc6c+GtMqkV8nmWdakunN7Qt/JbTcKlbH3HjIyXBy8gXDaEto5ABEBAAGJAh8EGAEIAAkF Ak6TJCgCGwwACgkQaMKH38aoAiZ4lg/+N2mkx5vsBmcsZVd3ys3sIsG18w6RcJZo5SGMxEBj t1UgyIXWI9lzpKCKIxKx0bskmEyMy4tPEDSRfZno/T7p1mU7hsM4owi/ic0aGBKP025Iok9G LKJcooP/A2c9dUV0FmygecRcbIAUaeJ27gotQkiJKbi0cl2gyTRlolKbC3R23K24LUhYfx4h pWj8CHoXEJrOdHO8Y0XH7059xzv5oxnXl2SD1dqA66INnX+vpW4TD2i+eQNPgfkECzKzGj+r KRfhdDZFBJj8/e131Y0t5cu+3Vok1FzBwgQqBnkA7dhBsQm3V0R8JTtMAqJGmyOcL+JCJAca 3Yi81yLyhmYzcRASLvJmoPTsDp2kZOdGr05Dt8aGPRJL33Jm+igfd8EgcDYtG6+F8MCBOult TTAu+QAijRPZv1KhEJXwUSke9HZvzo1tNTlY3h6plBsBufELu0mnqQvHZmfa5Ay99dF+dL1H WNp62+mTeHsX6v9EACH4S+Cw9Q1qJElFEu9/1vFNBmGY2vDv14gU2xEiS2eIvKiYl/b5Y85Q QLOHWV8up73KK5Qq/6bm4BqVd1rKGI9un8kezUQNGBKre2KKs6wquH8oynDP/baoYxEGMXBg GF/qjOC6OY+U7kNUW3N/A7J3M2VdOTLu3hVTzJMZdlMmmsg74azvZDV75dUigqXcwjE= Message-ID: Date: Wed, 13 Nov 2019 19:04:44 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/11/2019 18:34, Amir Goldstein wrote: > On Wed, Nov 13, 2019 at 7:57 PM Colin King wrote: >> >> From: Amir Goldstein >> >> In the past, overlayfs required that lower fs have non null >> uuid in order to support nfs export and decode copy up origin file handles. >> >> Commit 9df085f3c9a2 ("ovl: relax requirement for non null uuid of >> lower fs") relaxed this requirement for nfs export support, as long >> as uuid (even if null) is unique among all lower fs. >> >> However, said commit unintentionally also relaxed the non null uuid >> requirement for decoding copy up origin file handles, regardless of >> the unique uuid requirement. >> >> Amend this mistake by disabling decoding of copy up origin file handle >> from lower fs with a conflicting uuid. >> >> We still encode copy up origin file handles from those fs, because >> file handles like those already exist in the wild and because they >> might provide useful information in the future. >> >> [Colin Ian King] fixed the case of index=off,nfs_export=off >> >> Reported-by: Colin Ian King >> Link: https://lore.kernel.org/lkml/20191106234301.283006-1-colin.king@canonical.com/ >> Fixes: 9df085f3c9a2 ("ovl: relax requirement for non null uuid ...") >> Cc: stable@vger.kernel.org # v4.20+ >> Signed-off-by: Amir Goldstein >> Tested-by: Colin Ian King >> Signed-off-by: Colin Ian King ` >> --- >> >> V3: fix the following check: >> - if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt)) >> + if (!ofs->config.nfs_export && !ofs->upper_mnt) >> >> Add the index=off,nfs_export=off comment in the commit message >> >> --- >> fs/overlayfs/namei.c | 8 ++++++++ >> fs/overlayfs/ovl_entry.h | 2 ++ >> fs/overlayfs/super.c | 15 +++++++++++---- >> 3 files changed, 21 insertions(+), 4 deletions(-) >> >> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c >> index e9717c2f7d45..f47c591402d7 100644 >> --- a/fs/overlayfs/namei.c >> +++ b/fs/overlayfs/namei.c >> @@ -325,6 +325,14 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, >> int i; >> >> for (i = 0; i < ofs->numlower; i++) { >> + /* >> + * If lower fs uuid is not unique among lower fs we cannot match >> + * fh->uuid to layer. >> + */ >> + if (ofs->lower_layers[i].fsid && >> + ofs->lower_layers[i].fs->bad_uuid) >> + continue; >> + >> origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt, >> connected); >> if (origin) >> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h >> index a8279280e88d..28348c44ea5b 100644 >> --- a/fs/overlayfs/ovl_entry.h >> +++ b/fs/overlayfs/ovl_entry.h >> @@ -22,6 +22,8 @@ struct ovl_config { >> struct ovl_sb { >> struct super_block *sb; >> dev_t pseudo_dev; >> + /* Unusable (conflicting) uuid */ >> + bool bad_uuid; >> }; >> >> struct ovl_layer { >> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c >> index afbcb116a7f1..e53d399ce0af 100644 >> --- a/fs/overlayfs/super.c >> +++ b/fs/overlayfs/super.c >> @@ -1255,7 +1255,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) >> { >> unsigned int i; >> >> - if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt)) >> + if (!ofs->config.nfs_export && !ofs->upper_mnt) >> return true; >> >> for (i = 0; i < ofs->numlowerfs; i++) { >> @@ -1263,9 +1263,13 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) >> * We use uuid to associate an overlay lower file handle with a >> * lower layer, so we can accept lower fs with null uuid as long >> * as all lower layers with null uuid are on the same fs. >> + * if we detect multiple lower fs with the same uuid, we >> + * disable lower file handle decoding on all of them. >> */ >> - if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) >> + if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) { >> + ofs->lower_fs[i].bad_uuid = true; >> return false; >> + } >> } >> return true; >> } >> @@ -1277,6 +1281,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) >> unsigned int i; >> dev_t dev; >> int err; >> + bool bad_uuid = false; >> >> /* fsid 0 is reserved for upper fs even with non upper overlay */ >> if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb) >> @@ -1287,10 +1292,11 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) >> return i + 1; >> } >> >> - if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { >> + if (ofs->upper_mnt && !ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { > > Sorry I wasn't clear. > Miklos is right. the test ofs->upper_mnt here is bogus because > nfs_export could be enabled without upper. > The change you made in v3 to ovl_lower_uuid_ok() should be enough. OK, so the following is required for V4: + if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { > >> + bad_uuid = true; >> ofs->config.index = false; >> ofs->config.nfs_export = false; >> - pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n", >> + pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', enforcing index=off,nfs_export=off.\n", >> uuid_is_null(&sb->s_uuid) ? "null" : "conflicting", >> path->dentry); >> } >> @@ -1303,6 +1309,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) >> >> ofs->lower_fs[ofs->numlowerfs].sb = sb; >> ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev; >> + ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid; >> ofs->numlowerfs++; >> >> return ofs->numlowerfs; >> -- >> 2.20.1 >>