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From: Miklos Szeredi <miklos@szeredi.hu>
To: David Howells <dhowells@redhat.com>
Cc: viro@zeniv.linux.org.uk, 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
Subject: Re: [PATCH 15/18] fsinfo: Add an attribute that lists all the visible mounts in a namespace [ver #21]
Date: Tue, 4 Aug 2020 16:05:58 +0200	[thread overview]
Message-ID: <20200804140558.GF32719@miu.piliscsaba.redhat.com> (raw)
In-Reply-To: <159646191446.1784947.11228235431863356055.stgit@warthog.procyon.org.uk>

On Mon, Aug 03, 2020 at 02:38:34PM +0100, David Howells wrote:
> 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.

The change counters are currently conditional on CONFIG_MOUNT_NOTIFICATIONS.
Is this is intentional?

> 
> 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@redhat.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 122c12f9512b..1f2e06507244 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) {

This is missing locking and check added by commit 9f6c61f96f2d ("proc/mounts:
add cursor").

> +		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 81329de6905e..e40192d98648 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) */
> @@ -128,6 +129,8 @@ 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 */
> @@ -139,6 +142,7 @@ 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 374825ab85b0..596fa5e71762 100644
> --- a/samples/vfs/test-fsinfo.c
> +++ b/samples/vfs/test-fsinfo.c
> @@ -365,6 +365,27 @@ static void dump_fsinfo_generic_mount_children(void *reply, unsigned int size)
>  	       (unsigned long long)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", &params, (void **)&mp);
> +	if (mplen < 0)
> +		mp = "-";
> +
> +	printf("%5x %5x %12llx %10llu %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;
> @@ -492,6 +513,7 @@ 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),
> 
> 

  reply	other threads:[~2020-08-04 14:07 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-03 13:36 [PATCH 00/18] VFS: Filesystem information " David Howells
2020-08-03 13:36 ` [PATCH 01/18] fsinfo: Introduce a non-repeating system-unique superblock ID " David Howells
2020-08-04  9:34   ` Miklos Szeredi
2020-08-03 13:36 ` [PATCH 02/18] fsinfo: Add fsinfo() syscall to query filesystem information " David Howells
2020-08-04 10:16   ` Miklos Szeredi
2020-08-04 11:34   ` David Howells
2020-08-27 11:27   ` Michael Kerrisk (man-pages)
2020-08-03 13:36 ` [PATCH 03/18] fsinfo: Provide a bitmap of the features a filesystem supports " David Howells
2020-08-03 13:37 ` [PATCH 04/18] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-08-03 13:37 ` [PATCH 05/18] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-08-04 10:33   ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-08-04 10:41   ` Miklos Szeredi
2020-08-04 12:32     ` Ian Kent
2020-08-05 14:13   ` David Howells
2020-08-05 14:46     ` Miklos Szeredi
2020-08-05 15:30     ` David Howells
2020-08-05 19:33       ` Matthew Wilcox
2020-08-06  5:43         ` Ian Kent
2020-08-03 13:37 ` [PATCH 07/18] fsinfo: Allow mount information to be queried " David Howells
2020-08-03 13:37 ` [PATCH 08/18] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
2020-08-04 13:38   ` Miklos Szeredi
2020-08-05 15:37   ` David Howells
2020-08-05 17:19     ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 09/18] watch_queue: Mount event counters " David Howells
2020-08-03 13:37 ` [PATCH 10/18] fsinfo: Provide notification overrun handling support " David Howells
2020-08-04 13:56   ` Miklos Szeredi
2020-08-05  2:05     ` Ian Kent
2020-08-05  2:46       ` Ian Kent
2020-08-05  7:45         ` Miklos Szeredi
2020-08-05 11:23           ` Ian Kent
2020-08-05 11:27             ` Miklos Szeredi
2020-08-06  1:47               ` Ian Kent
2020-08-05 16:06   ` David Howells
2020-08-05 17:26     ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 11/18] fsinfo: sample: Mount listing program " David Howells
2020-08-03 13:38 ` [PATCH 12/18] fsinfo: Add API documentation " David Howells
2020-08-03 13:38 ` [PATCH 13/18] fsinfo: Add support for AFS " David Howells
2020-08-03 13:38 ` [PATCH 14/18] fsinfo: Add support to ext4 " David Howells
2020-08-03 13:38 ` [PATCH 15/18] fsinfo: Add an attribute that lists all the visible mounts in a namespace " David Howells
2020-08-04 14:05   ` Miklos Szeredi [this message]
2020-08-05  0:59     ` Ian Kent
2020-08-05 16:44   ` David Howells
2020-08-03 13:38 ` [PATCH 16/18] errseq: add a new errseq_scrape function " David Howells
2020-08-03 13:38 ` [PATCH 17/18] vfs: allow fsinfo to fetch the current state of s_wb_err " David Howells
2020-08-03 13:39 ` [PATCH 18/18] samples: add error state information to test-fsinfo.c " David Howells
2020-08-04 15:39 ` [PATCH 00/18] VFS: Filesystem information " James Bottomley
2020-08-04 19:18   ` Miklos Szeredi
2020-08-05 17:13 ` David Howells

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