From d93231a6bc8a452323d5fef16cca7107ce483a27 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lu=C3=ADs=20Henriques?= Date: Fri, 3 Jun 2022 14:29:09 +0100 Subject: [PATCH] ceph: prevent a client from exceeding the MDS maximum xattr size MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The MDS tries to enforce a limit on the total key/values in extended attributes. However, this limit is enforced only if doing a synchronous operation (MDS_OP_SETXATTR) -- if we're buffering the xattrs, the MDS doesn't have a chance to enforce these limits. This patch adds support for decoding the xattrs maximum size setting that is distributed in the mdsmap. Then, when setting an xattr, the kernel client will revert to do a synchronous operation if that maximum size is exceeded. While there, fix a dout() that would trigger a printk warning: [ 98.718078] ------------[ cut here ]------------ [ 98.719012] precision 65536 too large [ 98.719039] WARNING: CPU: 1 PID: 3755 at lib/vsprintf.c:2703 vsnprintf+0x5e3/0x600 ... Link: https://tracker.ceph.com/issues/55725 Signed-off-by: Luís Henriques Reviewed-by: Xiubo Li Signed-off-by: Ilya Dryomov --- fs/ceph/mdsmap.c | 22 ++++++++++++++++++---- fs/ceph/xattr.c | 12 ++++++++---- include/linux/ceph/mdsmap.h | 1 + 3 files changed, 27 insertions(+), 8 deletions(-) diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c index 30387733765d5..8d0a6d2c2da43 100644 --- a/fs/ceph/mdsmap.c +++ b/fs/ceph/mdsmap.c @@ -352,12 +352,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2) __decode_and_drop_type(p, end, u8, bad_ext); } if (mdsmap_ev >= 8) { - u32 name_len; /* enabled */ ceph_decode_8_safe(p, end, m->m_enabled, bad_ext); - ceph_decode_32_safe(p, end, name_len, bad_ext); - ceph_decode_need(p, end, name_len, bad_ext); - *p += name_len; + /* fs_name */ + ceph_decode_skip_string(p, end, bad_ext); } /* damaged */ if (mdsmap_ev >= 9) { @@ -370,6 +368,22 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2) } else { m->m_damaged = false; } + if (mdsmap_ev >= 17) { + /* balancer */ + ceph_decode_skip_string(p, end, bad_ext); + /* standby_count_wanted */ + ceph_decode_skip_32(p, end, bad_ext); + /* old_max_mds */ + ceph_decode_skip_32(p, end, bad_ext); + /* min_compat_client */ + ceph_decode_skip_8(p, end, bad_ext); + /* required_client_features */ + ceph_decode_skip_set(p, end, 64, bad_ext); + ceph_decode_64_safe(p, end, m->m_max_xattr_size, bad_ext); + } else { + /* This forces the usage of the (sync) SETXATTR Op */ + m->m_max_xattr_size = 0; + } bad_ext: dout("mdsmap_decode m_enabled: %d, m_damaged: %d, m_num_laggy: %d\n", !!m->m_enabled, !!m->m_damaged, m->m_num_laggy); diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c index f141f5246163d..f31350cda960b 100644 --- a/fs/ceph/xattr.c +++ b/fs/ceph/xattr.c @@ -1086,7 +1086,7 @@ static int ceph_sync_setxattr(struct inode *inode, const char *name, flags |= CEPH_XATTR_REMOVE; } - dout("setxattr value=%.*s\n", (int)size, value); + dout("setxattr value size: %zu\n", size); /* do request */ req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS); @@ -1184,8 +1184,14 @@ int __ceph_setxattr(struct inode *inode, const char *name, spin_lock(&ci->i_ceph_lock); retry: issued = __ceph_caps_issued(ci, NULL); - if (ci->i_xattrs.version == 0 || !(issued & CEPH_CAP_XATTR_EXCL)) + required_blob_size = __get_required_blob_size(ci, name_len, val_len); + if ((ci->i_xattrs.version == 0) || !(issued & CEPH_CAP_XATTR_EXCL) || + (required_blob_size > mdsc->mdsmap->m_max_xattr_size)) { + dout("%s do sync setxattr: version: %llu size: %d max: %llu\n", + __func__, ci->i_xattrs.version, required_blob_size, + mdsc->mdsmap->m_max_xattr_size); goto do_sync; + } if (!lock_snap_rwsem && !ci->i_head_snapc) { lock_snap_rwsem = true; @@ -1201,8 +1207,6 @@ int __ceph_setxattr(struct inode *inode, const char *name, ceph_cap_string(issued)); __build_xattrs(inode); - required_blob_size = __get_required_blob_size(ci, name_len, val_len); - if (!ci->i_xattrs.prealloc_blob || required_blob_size > ci->i_xattrs.prealloc_blob->alloc_len) { struct ceph_buffer *blob; diff --git a/include/linux/ceph/mdsmap.h b/include/linux/ceph/mdsmap.h index 523fd04528562..4c3e0648dc277 100644 --- a/include/linux/ceph/mdsmap.h +++ b/include/linux/ceph/mdsmap.h @@ -25,6 +25,7 @@ struct ceph_mdsmap { u32 m_session_timeout; /* seconds */ u32 m_session_autoclose; /* seconds */ u64 m_max_file_size; + u64 m_max_xattr_size; /* maximum size for xattrs blob */ u32 m_max_mds; /* expected up:active mds number */ u32 m_num_active_mds; /* actual up:active mds number */ u32 possible_max_rank; /* possible max rank index */