@@ -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,
@@ -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)
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: Amir Goldstein <amir73il@gmail.com> --- fs/notify/fanotify/fanotify_user.c | 61 +++++++++++++++++++++++++++++- include/linux/fanotify.h | 2 +- 2 files changed, 61 insertions(+), 2 deletions(-)