On Mon, Jun 24, 2019 at 03:10:20PM +0100, David Howells wrote: > Allow mount information, including information about the topology tree to > be queried with the fsinfo() system call. Usage of AT_FSINFO_MOUNTID_PATH > allows overlapping mounts to be queried.
Again, I really think that this doesn't need to land at the same time as the basic infrastructure for fsinfo()... > > To this end, four fsinfo() attributes are provided: > > (1) FSINFO_ATTR_MOUNT_INFO. > > This is a structure providing information about a mount, including: > > - Mounted superblock ID. > - Mount ID (as AT_FSINFO_MOUNTID_PATH). > - Parent mount ID. > - Mount attributes (eg. R/O, NOEXEC). > - Number of change notifications generated. > > Note that the parent mount ID is overridden to the ID of the queried > mount if the parent lies outside of the chroot or dfd tree. > > (2) FSINFO_ATTR_MOUNT_DEVNAME. > > This a string providing the device name associated with the mount. > > Note that the device name may be a path that lies outside of the root. > > (3) FSINFO_ATTR_MOUNT_CHILDREN. > > This produces an array of structures, one for each child and capped > with one for the argument mount (checked after listing all the > children). Each element contains the mount ID and the notification > counter of the respective mount object. > > (4) FSINFO_ATTR_MOUNT_SUBMOUNT. > > This is a 1D array of strings, indexed with struct fsinfo_params::Nth. > Each string is the relative pathname of the corresponding child > returned by FSINFO_ATTR_MOUNT_CHILDREN. > > Note that paths in the mount at the base of the tree (whether that be > dfd or chroot) are relative to the base of the tree, not the root > directory of that mount. > > Signed-off-by: David Howells <[email protected]> > --- > > fs/d_path.c | 2 > fs/fsinfo.c | 8 ++ > fs/internal.h | 9 ++ > fs/namespace.c | 177 > +++++++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/fsinfo.h | 28 +++++++ > samples/vfs/test-fsinfo.c | 47 +++++++++++ > 6 files changed, 267 insertions(+), 4 deletions(-) > > diff --git a/fs/d_path.c b/fs/d_path.c > index a7d0a96b35ce..89d77c264c5f 100644 > --- a/fs/d_path.c > +++ b/fs/d_path.c > @@ -227,7 +227,7 @@ static int prepend_unreachable(char **buffer, int *buflen) > return prepend(buffer, buflen, "(unreachable)", 13); > } > > -static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) > +void get_fs_root_rcu(struct fs_struct *fs, struct path *root) > { > unsigned seq; > > diff --git a/fs/fsinfo.c b/fs/fsinfo.c > index 3b218f9fedb7..61f00f375fd2 100644 > --- a/fs/fsinfo.c > +++ b/fs/fsinfo.c > @@ -348,6 +348,10 @@ int generic_fsinfo(struct path *path, struct > fsinfo_kparams *params) > case _genf(PARAM_SPECIFICATION, param_specification); > case _genf(PARAM_ENUM, param_enum); > case _genp(PARAMETERS, parameters); > + case _genp(MOUNT_INFO, mount_info); > + case _genp(MOUNT_DEVNAME, mount_devname); > + case _genp(MOUNT_CHILDREN, mount_children); > + case _genp(MOUNT_SUBMOUNT, mount_submount); > default: > return -EOPNOTSUPP; > } > @@ -627,6 +631,10 @@ static const struct fsinfo_attr_info > fsinfo_buffer_info[FSINFO_ATTR__NR] = { > FSINFO_STRUCT_N (PARAM_ENUM, param_enum), > FSINFO_OPAQUE (PARAMETERS, -), > FSINFO_OPAQUE (LSM_PARAMETERS, -), > + FSINFO_STRUCT (MOUNT_INFO, mount_info), > + FSINFO_STRING (MOUNT_DEVNAME, mount_devname), > + FSINFO_STRUCT_ARRAY (MOUNT_CHILDREN, mount_child), > + FSINFO_STRING_N (MOUNT_SUBMOUNT, mount_submount), > }; > > /** > diff --git a/fs/internal.h b/fs/internal.h > index 074b1c65e3bd..bb3d8efa7f49 100644 > --- a/fs/internal.h > +++ b/fs/internal.h > @@ -53,6 +53,11 @@ void __generic_write_end(struct inode *inode, loff_t pos, > unsigned copied, > */ > extern void __init chrdev_init(void); > > +/* > + * d_path.c > + */ > +extern void get_fs_root_rcu(struct fs_struct *fs, struct path *root); > + > /* > * fs_context.c > */ > @@ -98,6 +103,10 @@ extern void __mnt_drop_write_file(struct file *); > > extern void dissolve_on_fput(struct vfsmount *); > extern int lookup_mount_object(struct path *, int, struct path *); > +extern int fsinfo_generic_mount_info(struct path *, struct fsinfo_kparams *); > +extern int fsinfo_generic_mount_devname(struct path *, struct fsinfo_kparams > *); > +extern int fsinfo_generic_mount_children(struct path *, struct > fsinfo_kparams *); > +extern int fsinfo_generic_mount_submount(struct path *, struct > fsinfo_kparams *); > > /* > * fs_struct.c > diff --git a/fs/namespace.c b/fs/namespace.c > index 1450faab96b9..2ec7d9d1905a 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -29,6 +29,7 @@ > #include <linux/sched/task.h> > #include <uapi/linux/mount.h> > #include <linux/fs_context.h> > +#include <linux/fsinfo.h> > > #include "pnode.h" > #include "internal.h" > @@ -4112,3 +4113,179 @@ int lookup_mount_object(struct path *root, int > mnt_id, struct path *_mntpt) > unlock_mount_hash(); > goto out_unlock; > } > + > +#ifdef CONFIG_FSINFO > +int fsinfo_generic_mount_info(struct path *path, struct fsinfo_kparams > *params) > +{ > + struct fsinfo_mount_info *p = params->buffer; > + struct super_block *sb; > + struct mount *m; > + struct path root; > + unsigned int flags; > + > + if (!path->mnt) > + return -ENODATA; > + > + m = real_mount(path->mnt); > + sb = m->mnt.mnt_sb; > + > + p->f_sb_id = sb->s_unique_id; > + p->mnt_id = m->mnt_id; > + p->parent_id = m->mnt_parent->mnt_id; > + p->notify_counter = atomic_read(&m->mnt_notify_counter); > + > + get_fs_root(current->fs, &root); > + if (path->mnt == root.mnt) { > + p->parent_id = p->mnt_id; > + } else { > + rcu_read_lock(); > + if (!are_paths_connected(&root, path)) > + p->parent_id = p->mnt_id; > + rcu_read_unlock(); > + } > + if (IS_MNT_SHARED(m)) > + p->group_id = m->mnt_group_id; > + if (IS_MNT_SLAVE(m)) { > + int master = m->mnt_master->mnt_group_id; > + int dom = get_dominating_id(m, &root); > + p->master_id = master; > + if (dom && dom != master) > + p->from_id = dom; > + } > + path_put(&root); > + > + flags = READ_ONCE(m->mnt.mnt_flags); > + if (flags & MNT_READONLY) > + p->attr |= MOUNT_ATTR_RDONLY; > + if (flags & MNT_NOSUID) > + p->attr |= MOUNT_ATTR_NOSUID; > + if (flags & MNT_NODEV) > + p->attr |= MOUNT_ATTR_NODEV; > + if (flags & MNT_NOEXEC) > + p->attr |= MOUNT_ATTR_NOEXEC; > + if (flags & MNT_NODIRATIME) > + p->attr |= MOUNT_ATTR_NODIRATIME; > + > + if (flags & MNT_NOATIME) > + p->attr |= MOUNT_ATTR_NOATIME; > + else if (flags & MNT_RELATIME) > + p->attr |= MOUNT_ATTR_RELATIME; > + else > + p->attr |= MOUNT_ATTR_STRICTATIME; > + return sizeof(*p); > +} > + > +int fsinfo_generic_mount_devname(struct path *path, struct fsinfo_kparams > *params) > +{ > + struct mount *m; > + size_t len; > + > + if (!path->mnt) > + return -ENODATA; > + > + m = real_mount(path->mnt); > + len = strlen(m->mnt_devname); > + memcpy(params->buffer, m->mnt_devname, len); > + return len; > +} > + > +/* > + * Store a mount record into the fsinfo buffer. > + */ > +static void store_mount_fsinfo(struct fsinfo_kparams *params, > + struct fsinfo_mount_child *child) > +{ > + unsigned int usage = params->usage; > + unsigned int total = sizeof(*child); > + > + if (params->usage >= INT_MAX) > + return; > + params->usage = usage + total; > + if (params->buffer && params->usage <= params->buf_size) > + memcpy(params->buffer + usage, child, total); > +} > + > +/* > + * Return information about the submounts relative to path. > + */ > +int fsinfo_generic_mount_children(struct path *path, struct fsinfo_kparams > *params) > +{ > + struct fsinfo_mount_child record; > + struct mount *m, *child; > + > + if (!path->mnt) > + return -ENODATA; > + > + m = real_mount(path->mnt); > + > + rcu_read_lock(); > + list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) { > + if (child->mnt_parent != m) > + continue; > + record.mnt_id = child->mnt_id; > + record.notify_counter = atomic_read(&child->mnt_notify_counter); > + store_mount_fsinfo(params, &record); > + } > + rcu_read_unlock(); > + > + /* End the list with a copy of the parameter mount's details so that > + * userspace can quickly check for changes. > + */ > + record.mnt_id = m->mnt_id; > + record.notify_counter = atomic_read(&m->mnt_notify_counter); > + store_mount_fsinfo(params, &record); > + return params->usage; > +} > + > +/* > + * Return the path of the Nth submount relative to path. This is derived > from > + * d_path(), but the root determination is more complicated. > + */ > +int fsinfo_generic_mount_submount(struct path *path, struct fsinfo_kparams > *params) > +{ > + struct mountpoint *mp; > + struct mount *m, *child; > + struct path mountpoint, root; > + unsigned int n = params->Nth; > + size_t len; > + void *p; > + > + if (!path->mnt) > + return -ENODATA; > + > + rcu_read_lock(); > + > + m = real_mount(path->mnt); > + list_for_each_entry_rcu(child, &m->mnt_mounts, mnt_child) { > + mp = READ_ONCE(child->mnt_mp); > + if (child->mnt_parent != m || !mp) > + continue; > + if (n-- == 0) > + goto found; > + } > + rcu_read_unlock(); > + return -ENODATA; > + > +found: > + mountpoint.mnt = path->mnt; > + mountpoint.dentry = READ_ONCE(mp->m_dentry); > + > + get_fs_root_rcu(current->fs, &root); > + if (root.mnt != path->mnt) { > + root.mnt = path->mnt; > + root.dentry = path->mnt->mnt_root; > + } > + > + p = __d_path(&mountpoint, &root, params->buffer, params->buf_size); > + rcu_read_unlock(); > + > + if (IS_ERR(p)) > + return PTR_ERR(p); > + if (!p) > + return -EPERM; > + > + len = (params->buffer + params->buf_size) - p; > + memmove(params->buffer, p, len); > + return len; > +} > +#endif /* CONFIG_FSINFO */ > diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h > index bae0bdc9ace9..88e1d004ac6c 100644 > --- a/include/uapi/linux/fsinfo.h > +++ b/include/uapi/linux/fsinfo.h > @@ -32,6 +32,10 @@ enum fsinfo_attribute { > FSINFO_ATTR_PARAM_ENUM = 14, /* Nth enum-to-val */ > FSINFO_ATTR_PARAMETERS = 15, /* Mount parameters (large > string) */ > FSINFO_ATTR_LSM_PARAMETERS = 16, /* LSM Mount parameters (large > string) */ > + FSINFO_ATTR_MOUNT_INFO = 17, /* Mount object information */ > + FSINFO_ATTR_MOUNT_DEVNAME = 18, /* Mount object device name > (string) */ > + FSINFO_ATTR_MOUNT_CHILDREN = 19, /* Submount list (array) */ > + FSINFO_ATTR_MOUNT_SUBMOUNT = 20, /* Relative path of Nth > submount (string) */ > FSINFO_ATTR__NR > }; > > @@ -276,4 +280,28 @@ struct fsinfo_param_enum { > char name[252]; /* Name of the enum value */ > }; > > +/* > + * Information struct for fsinfo(FSINFO_ATTR_MOUNT_INFO). > + */ > +struct fsinfo_mount_info { > + __u64 f_sb_id; /* Superblock ID */ > + __u32 mnt_id; /* Mount identifier (use with > AT_FSINFO_MOUNTID_PATH) */ > + __u32 parent_id; /* Parent mount identifier */ > + __u32 group_id; /* Mount group ID */ > + __u32 master_id; /* Slave master group ID */ > + __u32 from_id; /* Slave propagated from ID */ > + __u32 attr; /* MOUNT_ATTR_* flags */ > + __u32 notify_counter; /* Number of notifications generated. */ > + __u32 __reserved[1]; > +}; > + > +/* > + * Information struct element for fsinfo(FSINFO_ATTR_MOUNT_CHILDREN). > + * - An extra element is placed on the end representing the parent mount. > + */ > +struct fsinfo_mount_child { > + __u32 mnt_id; /* Mount identifier (use with > AT_FSINFO_MOUNTID_PATH) */ > + __u32 notify_counter; /* Number of notifications generated on > mount. */ > +}; > + > #endif /* _UAPI_LINUX_FSINFO_H */ > diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c > index fadc5e1384fc..ab32a15d4c5b 100644 > --- a/samples/vfs/test-fsinfo.c > +++ b/samples/vfs/test-fsinfo.c > @@ -21,10 +21,10 @@ > #include <errno.h> > #include <time.h> > #include <math.h> > -#include <fcntl.h> > #include <sys/syscall.h> > #include <linux/fsinfo.h> > #include <linux/socket.h> > +#include <linux/fcntl.h> > #include <sys/stat.h> > #include <arpa/inet.h> > > @@ -83,6 +83,10 @@ static const struct fsinfo_attr_info > fsinfo_buffer_info[FSINFO_ATTR__NR] = { > FSINFO_STRUCT_N (PARAM_ENUM, param_enum), > FSINFO_OVERLARGE (PARAMETERS, -), > FSINFO_OVERLARGE (LSM_PARAMETERS, -), > + FSINFO_STRUCT (MOUNT_INFO, mount_info), > + FSINFO_STRING (MOUNT_DEVNAME, mount_devname), > + FSINFO_STRUCT_ARRAY (MOUNT_CHILDREN, mount_child), > + FSINFO_STRING_N (MOUNT_SUBMOUNT, mount_submount), > }; > > #define FSINFO_NAME(X,Y) [FSINFO_ATTR_##X] = #Y > @@ -104,6 +108,10 @@ static const char *fsinfo_attr_names[FSINFO_ATTR__NR] = { > FSINFO_NAME (PARAM_ENUM, param_enum), > FSINFO_NAME (PARAMETERS, parameters), > FSINFO_NAME (LSM_PARAMETERS, lsm_parameters), > + FSINFO_NAME (MOUNT_INFO, mount_info), > + FSINFO_NAME (MOUNT_DEVNAME, mount_devname), > + FSINFO_NAME (MOUNT_CHILDREN, mount_children), > + FSINFO_NAME (MOUNT_SUBMOUNT, mount_submount), > }; > > union reply { > @@ -116,6 +124,8 @@ union reply { > struct fsinfo_capabilities caps; > struct fsinfo_timestamp_info timestamps; > struct fsinfo_volume_uuid uuid; > + struct fsinfo_mount_info mount_info; > + struct fsinfo_mount_child mount_children[1]; > }; > > static void dump_hex(unsigned int *data, int from, int to) > @@ -319,6 +329,29 @@ static void dump_attr_VOLUME_UUID(union reply *r, int > size) > f->uuid[14], f->uuid[15]); > } > > +static void dump_attr_MOUNT_INFO(union reply *r, int size) > +{ > + struct fsinfo_mount_info *f = &r->mount_info; > + > + printf("\n"); > + printf("\tsb_id : %llx\n", (unsigned long long)f->f_sb_id); > + printf("\tmnt_id : %x\n", f->mnt_id); > + printf("\tparent : %x\n", f->parent_id); > + printf("\tgroup : %x\n", f->group_id); > + printf("\tattr : %x\n", f->attr); > + printf("\tnotifs : %x\n", f->notify_counter); > +} > + > +static void dump_attr_MOUNT_CHILDREN(union reply *r, int size) > +{ > + struct fsinfo_mount_child *f = r->mount_children; > + int i = 0; > + > + printf("\n"); > + for (; size >= sizeof(*f); size -= sizeof(*f), f++) > + printf("\t[%u] %8x %8x\n", i++, f->mnt_id, f->notify_counter); > +} > + > /* > * > */ > @@ -334,6 +367,8 @@ static const dumper_t fsinfo_attr_dumper[FSINFO_ATTR__NR] > = { > FSINFO_DUMPER(CAPABILITIES), > FSINFO_DUMPER(TIMESTAMP_INFO), > FSINFO_DUMPER(VOLUME_UUID), > + FSINFO_DUMPER(MOUNT_INFO), > + FSINFO_DUMPER(MOUNT_CHILDREN), > }; > > static void dump_fsinfo(enum fsinfo_attribute attr, > @@ -536,16 +571,21 @@ int main(int argc, char **argv) > unsigned int attr; > int raw = 0, opt, Nth, Mth; > > - while ((opt = getopt(argc, argv, "adlr"))) { > + while ((opt = getopt(argc, argv, "Madlr"))) { > switch (opt) { > + case 'M': > + params.at_flags = AT_FSINFO_MOUNTID_PATH; > + continue; > case 'a': > params.at_flags |= AT_NO_AUTOMOUNT; > + params.at_flags &= ~AT_FSINFO_MOUNTID_PATH; > continue; > case 'd': > debug = true; > continue; > case 'l': > params.at_flags &= ~AT_SYMLINK_NOFOLLOW; > + params.at_flags &= ~AT_FSINFO_MOUNTID_PATH; > continue; > case 'r': > raw = 1; > @@ -558,7 +598,8 @@ int main(int argc, char **argv) > argv += optind; > > if (argc != 1) { > - printf("Format: test-fsinfo [-alr] <file>\n"); > + printf("Format: test-fsinfo [-adlr] <file>\n"); > + printf("Format: test-fsinfo [-dr] -M <mnt_id>\n"); > exit(2); > } > >
