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Commit a8b13aa2 authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fanotify: enable FAN_REPORT_FID init flag 



When setting up an fanotify listener, user may request to get fid
information in event instead of an open file descriptor.

The fid obtained with event on a watched object contains the file
handle returned by name_to_handle_at(2) and fsid returned by statfs(2).

Restrict FAN_REPORT_FID to class FAN_CLASS_NOTIF, because we have have
no good reason to support reporting fid on permission events.

When setting a mark, we need to make sure that the filesystem
supports encoding file handles with name_to_handle_at(2) and that
statfs(2) encodes a non-zero fsid.

Cc: <linux-api@vger.kernel.org>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 5e469c83

fs/notify/fanotify/fanotify_user.c

+60 −1
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ 
#include <linux/compat.h>

#include <linux/sched/signal.h>

#include <linux/memcontrol.h>

#include <linux/statfs.h>

#include <linux/exportfs.h>



#include <asm/ioctls.h>
@@ -768,6 +770,10 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) 
		return -EINVAL;

	}



	if ((flags & FAN_REPORT_FID) &&

	    (flags & FANOTIFY_CLASS_BITS) != FAN_CLASS_NOTIF)

		return -EINVAL;



	user = get_current_user();

	if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {

		free_uid(user);
@@ -854,6 +860,52 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) 
	return fd;

}



/* Check if filesystem can encode a unique fid */

static int fanotify_test_fid(struct path *path)

{

	struct kstatfs stat, root_stat;

	struct path root = {

		.mnt = path->mnt,

		.dentry = path->dentry->d_sb->s_root,

	};

	int err;



	/*

	 * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).

	 */

	err = vfs_statfs(path, &stat);

	if (err)

		return err;



	if (!stat.f_fsid.val[0] && !stat.f_fsid.val[1])

		return -ENODEV;



	/*

	 * Make sure path is not inside a filesystem subvolume (e.g. btrfs)

	 * which uses a different fsid than sb root.

	 */

	err = vfs_statfs(&root, &root_stat);

	if (err)

		return err;



	if (root_stat.f_fsid.val[0] != stat.f_fsid.val[0] ||

	    root_stat.f_fsid.val[1] != stat.f_fsid.val[1])

		return -EXDEV;



	/*

	 * We need to make sure that the file system supports at least

	 * encoding a file handle so user can use name_to_handle_at() to

	 * compare fid returned with event to the file handle of watched

	 * objects. However, name_to_handle_at() requires that the

	 * filesystem also supports decoding file handles.

	 */

	if (!path->dentry->d_sb->s_export_op ||

	    !path->dentry->d_sb->s_export_op->fh_to_dentry)

		return -EOPNOTSUPP;



	return 0;

}



static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,

			    int dfd, const char  __user *pathname)

{
@@ -939,6 +991,12 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	if (ret)

		goto fput_and_out;



	if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {

		ret = fanotify_test_fid(&path);

		if (ret)

			goto path_put_and_out;

	}



	/* inode held in place by reference to path; group by fget on fd */

	if (mark_type == FAN_MARK_INODE)

		inode = path.dentry->d_inode;
@@ -967,6 +1025,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
		ret = -EINVAL;

	}



path_put_and_out:

	path_put(&path);

fput_and_out:

	fdput(f);
@@ -1003,7 +1062,7 @@ COMPAT_SYSCALL_DEFINE6(fanotify_mark, 
 */

static int __init fanotify_user_setup(void)

{

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 7);

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 8);

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);



	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,

include/linux/fanotify.h

+1 −1
Original line number Diff line number Diff line
@@ -19,7 +19,7 @@ 
				 FAN_CLASS_PRE_CONTENT)



#define FANOTIFY_INIT_FLAGS	(FANOTIFY_CLASS_BITS | \

				 FAN_REPORT_TID | \

				 FAN_REPORT_TID | FAN_REPORT_FID | \

				 FAN_CLOEXEC | FAN_NONBLOCK | \

				 FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS)