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Date: Fri, 24 Jul 2020 14:36:54 +0100
From: David Howells <dhowells@...hat.com>
To: torvalds@...ux-foundation.org, viro@...iv.linux.org.uk
Cc: dhowells@...hat.com, raven@...maw.net, mszeredi@...hat.com,
christian@...uner.io, jannh@...gle.com, darrick.wong@...cle.com,
kzak@...hat.com, jlayton@...hat.com, linux-api@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 14/17] fsinfo: Add an attribute that lists all the visible
mounts in a namespace [ver #20]
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 <dhowells@...hat.com>
---
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),
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