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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 14/17] fsinfo: Add an attribute that lists all the visible mounts in a namespace [ver #20] From: David Howells To: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, 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: Fri, 24 Jul 2020 14:36:54 +0100 Message-ID: <159559781457.2144584.16532913492732387261.stgit@warthog.procyon.org.uk> In-Reply-To: <159559768062.2144584.13583793543173131929.stgit@warthog.procyon.org.uk> References: <159559768062.2144584.13583793543173131929.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a filesystem attribute that exports a list of all the visible mounts in a namespace, given the caller's chroot setting. The returned list is an array of: struct fsinfo_mount_child { __u64 mnt_unique_id; __u32 mnt_id; __u32 parent_id; __u32 mnt_notify_sum; __u32 sb_notify_sum; }; where each element contains a once-in-a-system-lifetime unique ID, the mount ID (which may get reused), the parent mount ID and sums of the notification/change counters for the mount and its superblock. This works with a read lock on the namespace_sem, but ideally would do it under the RCU read lock only. Signed-off-by: David Howells --- fs/fsinfo.c | 1 + fs/internal.h | 1 + fs/namespace.c | 37 +++++++++++++++++++++++++++++++++++++ include/uapi/linux/fsinfo.h | 4 ++++ samples/vfs/test-fsinfo.c | 22 ++++++++++++++++++++++ 5 files changed, 65 insertions(+) diff --git a/fs/fsinfo.c b/fs/fsinfo.c index 0540cce89555..f230124ffdf5 100644 --- a/fs/fsinfo.c +++ b/fs/fsinfo.c @@ -296,6 +296,7 @@ static const struct fsinfo_attribute fsinfo_common_attributes[] = { FSINFO_STRING (FSINFO_ATTR_MOUNT_POINT, fsinfo_generic_mount_point), FSINFO_STRING (FSINFO_ATTR_MOUNT_POINT_FULL, fsinfo_generic_mount_point_full), FSINFO_LIST (FSINFO_ATTR_MOUNT_CHILDREN, fsinfo_generic_mount_children), + FSINFO_LIST (FSINFO_ATTR_MOUNT_ALL, fsinfo_generic_mount_all), {} }; diff --git a/fs/internal.h b/fs/internal.h index cb5edcc7125a..267b4aaf0271 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -102,6 +102,7 @@ extern int fsinfo_generic_mount_topology(struct path *, struct fsinfo_context *) extern int fsinfo_generic_mount_point(struct path *, struct fsinfo_context *); extern int fsinfo_generic_mount_point_full(struct path *, struct fsinfo_context *); extern int fsinfo_generic_mount_children(struct path *, struct fsinfo_context *); +extern int fsinfo_generic_mount_all(struct path *, struct fsinfo_context *); /* * fs_struct.c diff --git a/fs/namespace.c b/fs/namespace.c index 2205b1e52a41..7e2b66eb4f75 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -4494,4 +4494,41 @@ int fsinfo_generic_mount_children(struct path *path, struct fsinfo_context *ctx) return ctx->usage; } +/* + * Return information about all the mounts in the namespace referenced by the + * path. + */ +int fsinfo_generic_mount_all(struct path *path, struct fsinfo_context *ctx) +{ + struct mnt_namespace *ns; + struct mount *m, *p; + struct path chroot; + bool allow; + + m = real_mount(path->mnt); + ns = m->mnt_ns; + + get_fs_root(current->fs, &chroot); + rcu_read_lock(); + allow = are_paths_connected(&chroot, path) || capable(CAP_SYS_ADMIN); + rcu_read_unlock(); + path_put(&chroot); + if (!allow) + return -EPERM; + + down_read(&namespace_sem); + + list_for_each_entry(p, &ns->list, mnt_list) { + struct path mnt_root; + + mnt_root.mnt = &p->mnt; + mnt_root.dentry = p->mnt.mnt_root; + if (are_paths_connected(path, &mnt_root)) + fsinfo_store_mount(ctx, p, p == m); + } + + up_read(&namespace_sem); + return ctx->usage; +} + #endif /* CONFIG_FSINFO */ diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h index e53bb50a61e2..6f71d66d1112 100644 --- a/include/uapi/linux/fsinfo.h +++ b/include/uapi/linux/fsinfo.h @@ -37,6 +37,7 @@ #define FSINFO_ATTR_MOUNT_POINT_FULL 0x203 /* Absolute path of mount (string) */ #define FSINFO_ATTR_MOUNT_TOPOLOGY 0x204 /* Mount object topology */ #define FSINFO_ATTR_MOUNT_CHILDREN 0x205 /* Children of this mount (list) */ +#define FSINFO_ATTR_MOUNT_ALL 0x206 /* List all mounts in a namespace (list) */ #define FSINFO_ATTR_AFS_CELL_NAME 0x300 /* AFS cell name (string) */ #define FSINFO_ATTR_AFS_SERVER_NAME 0x301 /* Name of the Nth server (string) */ @@ -129,6 +130,8 @@ struct fsinfo_mount_topology { /* * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_CHILDREN). * - An extra element is placed on the end representing the parent mount. + * + * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_ALL). */ struct fsinfo_mount_child { __u64 mnt_unique_id; /* Kernel-lifetime unique mount ID */ @@ -140,6 +143,7 @@ struct fsinfo_mount_child { }; #define FSINFO_ATTR_MOUNT_CHILDREN__STRUCT struct fsinfo_mount_child +#define FSINFO_ATTR_MOUNT_ALL__STRUCT struct fsinfo_mount_child /* * Information struct for fsinfo(FSINFO_ATTR_STATFS). diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c index 462dae1d0423..5209b6a44fb0 100644 --- a/samples/vfs/test-fsinfo.c +++ b/samples/vfs/test-fsinfo.c @@ -363,6 +363,27 @@ static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size) r->mnt_notify_sum, mp); } +static void dump_fsinfo_generic_mount_all(void *reply, unsigned int size) +{ + struct fsinfo_mount_child *r = reply; + ssize_t mplen; + char path[32], *mp; + + struct fsinfo_params params = { + .flags = FSINFO_FLAGS_QUERY_MOUNT, + .request = FSINFO_ATTR_MOUNT_POINT_FULL, + }; + + sprintf(path, "%u", r->mnt_id); + mplen = get_fsinfo(path, "FSINFO_ATTR_MOUNT_POINT_FULL", ¶ms, (void **)&mp); + if (mplen < 0) + mp = "-"; + + printf("%5x %5x %12llx %10u %s\n", + r->mnt_id, r->parent_id, (unsigned long long)r->mnt_unique_id, + r->mnt_notify_sum, mp); +} + static void dump_afs_fsinfo_server_address(void *reply, unsigned int size) { struct fsinfo_afs_server_address *f = reply; @@ -490,6 +511,7 @@ static const struct fsinfo_attribute fsinfo_attributes[] = { FSINFO_STRING_N (FSINFO_ATTR_MOUNT_POINT, string), FSINFO_STRING_N (FSINFO_ATTR_MOUNT_POINT_FULL, string), FSINFO_LIST (FSINFO_ATTR_MOUNT_CHILDREN, fsinfo_generic_mount_children), + FSINFO_LIST (FSINFO_ATTR_MOUNT_ALL, fsinfo_generic_mount_all), FSINFO_STRING (FSINFO_ATTR_AFS_CELL_NAME, string), FSINFO_STRING (FSINFO_ATTR_AFS_SERVER_NAME, string),