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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 04/18] fsinfo: Allow retrieval of superblock devname, options and stats [ver #21] From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, torvalds@linux-foundation.org, raven@themaw.net, mszeredi@redhat.com, christian@brauner.io, jannh@google.com, darrick.wong@oracle.com, kzak@redhat.com, jlayton@redhat.com, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 03 Aug 2020 14:37:00 +0100 Message-ID: <159646181998.1784947.15915025004856012744.stgit@warthog.procyon.org.uk> In-Reply-To: <159646178122.1784947.11705396571718464082.stgit@warthog.procyon.org.uk> References: <159646178122.1784947.11705396571718464082.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Provide fsinfo() attributes to retrieve superblock device name, options, and statistics in string form. The following attributes are defined: FSINFO_ATTR_SOURCE - Mount-specific device name FSINFO_ATTR_CONFIGURATION - Mount options FSINFO_ATTR_FS_STATISTICS - Filesystem statistics FSINFO_ATTR_SOURCE could be made indexable by params->Nth to handle the case where there is more than one source (e.g. the bcachefs filesystem). Signed-off-by: David Howells --- fs/fsinfo.c | 39 +++++++++++++++++++++++++++++++++++++++ fs/internal.h | 2 ++ fs/namespace.c | 41 +++++++++++++++++++++++++++++++++++++++++ include/uapi/linux/fsinfo.h | 3 +++ samples/vfs/test-fsinfo.c | 4 ++++ 5 files changed, 89 insertions(+) diff --git a/fs/fsinfo.c b/fs/fsinfo.c index 79c222d465d8..aef7a736e8fc 100644 --- a/fs/fsinfo.c +++ b/fs/fsinfo.c @@ -231,6 +231,42 @@ static int fsinfo_generic_volume_id(struct path *path, struct fsinfo_context *ct return fsinfo_string(path->dentry->d_sb->s_id, ctx); } +/* + * Retrieve the superblock configuration (mount options) as a comma-separated + * string. The initial comma is stripped off and NUL termination is added. + */ +static int fsinfo_generic_seq_read(struct path *path, struct fsinfo_context *ctx) +{ + struct super_block *sb = path->dentry->d_sb; + struct seq_file m = { + .buf = ctx->buffer, + .size = ctx->buf_size - 1, + }; + int ret = 0; + + switch (ctx->requested_attr) { + case FSINFO_ATTR_CONFIGURATION: + seq_puts(&m, sb_rdonly(sb) ? "ro" : "rw"); + ret = security_sb_show_options(&m, sb); + if (!ret && sb->s_op->show_options) + ret = sb->s_op->show_options(&m, path->mnt->mnt_root); + break; + + case FSINFO_ATTR_FS_STATISTICS: + if (sb->s_op->show_stats) + ret = sb->s_op->show_stats(&m, path->mnt->mnt_root); + break; + } + + if (ret < 0) + return ret; + if (seq_has_overflowed(&m)) + return ctx->buf_size + PAGE_SIZE; + + ((char *)ctx->buffer)[ctx->skip + m.count] = 0; + return m.count + 1; +} + static const struct fsinfo_attribute fsinfo_common_attributes[] = { FSINFO_VSTRUCT (FSINFO_ATTR_STATFS, fsinfo_generic_statfs), FSINFO_VSTRUCT (FSINFO_ATTR_IDS, fsinfo_generic_ids), @@ -240,6 +276,9 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = { FSINFO_STRING (FSINFO_ATTR_VOLUME_ID, fsinfo_generic_volume_id), FSINFO_VSTRUCT (FSINFO_ATTR_VOLUME_UUID, fsinfo_generic_volume_uuid), FSINFO_VSTRUCT (FSINFO_ATTR_FEATURES, fsinfo_generic_features), + FSINFO_STRING (FSINFO_ATTR_SOURCE, fsinfo_generic_mount_source), + FSINFO_STRING (FSINFO_ATTR_CONFIGURATION, fsinfo_generic_seq_read), + FSINFO_STRING (FSINFO_ATTR_FS_STATISTICS, fsinfo_generic_seq_read), FSINFO_LIST (FSINFO_ATTR_FSINFO_ATTRIBUTES, (void *)123UL), FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, (void *)123UL), diff --git a/fs/internal.h b/fs/internal.h index ea60d864a8cb..0b57da498f06 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -89,6 +89,8 @@ extern int __mnt_want_write_file(struct file *); extern void __mnt_drop_write_file(struct file *); extern void dissolve_on_fput(struct vfsmount *); +extern int fsinfo_generic_mount_source(struct path *, struct fsinfo_context *); + /* * fs_struct.c */ diff --git a/fs/namespace.c b/fs/namespace.c index 73ff5bf0c9af..ead8d1a16610 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -30,6 +30,7 @@ #include #include #include +#include #include "pnode.h" #include "internal.h" @@ -4111,3 +4112,43 @@ const struct proc_ns_operations mntns_operations = { .install = mntns_install, .owner = mntns_owner, }; + +#ifdef CONFIG_FSINFO +static inline void mangle(struct seq_file *m, const char *s) +{ + seq_escape(m, s, " \t\n\\"); +} + +/* + * Return the mount source/device name as seen from this mountpoint. Shared + * mounts may vary here and the filesystem is permitted to substitute its own + * rendering. + */ +int fsinfo_generic_mount_source(struct path *path, struct fsinfo_context *ctx) +{ + struct super_block *sb = path->mnt->mnt_sb; + struct mount *mnt = real_mount(path->mnt); + struct seq_file m = { + .buf = ctx->buffer, + .size = ctx->buf_size - 1, + }; + int ret; + + if (sb->s_op->show_devname) { + ret = sb->s_op->show_devname(&m, mnt->mnt.mnt_root); + if (ret < 0) + return ret; + } else { + if (!mnt->mnt_devname) + return fsinfo_string("none", ctx); + mangle(&m, mnt->mnt_devname); + } + + if (seq_has_overflowed(&m)) + return ctx->buf_size + PAGE_SIZE; + + ((char *)ctx->buffer)[m.count] = 0; + return m.count + 1; +} + +#endif /* CONFIG_FSINFO */ diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h index b8b2c836267b..a27e92b68266 100644 --- a/include/uapi/linux/fsinfo.h +++ b/include/uapi/linux/fsinfo.h @@ -24,6 +24,9 @@ #define FSINFO_ATTR_VOLUME_UUID 0x06 /* Volume UUID (LE uuid) */ #define FSINFO_ATTR_VOLUME_NAME 0x07 /* Volume name (string) */ #define FSINFO_ATTR_FEATURES 0x08 /* Filesystem features (bits) */ +#define FSINFO_ATTR_SOURCE 0x09 /* Superblock source/device name (string) */ +#define FSINFO_ATTR_CONFIGURATION 0x0a /* Superblock configuration/options (string) */ +#define FSINFO_ATTR_FS_STATISTICS 0x0b /* Superblock filesystem statistics (string) */ #define FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO 0x100 /* Information about attr N (for path) */ #define FSINFO_ATTR_FSINFO_ATTRIBUTES 0x101 /* List of supported attrs (for path) */ diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c index c5932109f683..634f30b7e67f 100644 --- a/samples/vfs/test-fsinfo.c +++ b/samples/vfs/test-fsinfo.c @@ -364,6 +364,10 @@ static const struct fsinfo_attribute fsinfo_attributes[] = { FSINFO_STRING (FSINFO_ATTR_VOLUME_ID, string), FSINFO_VSTRUCT (FSINFO_ATTR_VOLUME_UUID, fsinfo_generic_volume_uuid), FSINFO_STRING (FSINFO_ATTR_VOLUME_NAME, string), + FSINFO_STRING (FSINFO_ATTR_SOURCE, string), + FSINFO_STRING (FSINFO_ATTR_CONFIGURATION, string), + FSINFO_STRING (FSINFO_ATTR_FS_STATISTICS, string), + FSINFO_VSTRUCT_N(FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, fsinfo_meta_attribute_info), FSINFO_LIST (FSINFO_ATTR_FSINFO_ATTRIBUTES, fsinfo_meta_attributes), {}