7 files changed, 119 insertions, 17 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index cb1026181bdc..6c82e5bac039 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -131,7 +131,7 @@ SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 SYSCALL_DEFINE1(dup, unsigned int, fildes)
 {
         int ret = -EBADF;
-        struct file *file = fget(fildes);
+        struct file *file = fget_raw(fildes);
 
         if (file) {
                 ret = get_unused_fd();
@@ -426,15 +426,35 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
         return err;
 }
 
+static int check_fcntl_cmd(unsigned cmd)
+{
+        switch (cmd) {
+        case F_DUPFD:
+        case F_DUPFD_CLOEXEC:
+        case F_GETFD:
+        case F_SETFD:
+        case F_GETFL:
+                return 1;
+        }
+        return 0;
+}
+
 SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
 {       
         struct file *filp;
         long err = -EBADF;
 
-        filp = fget(fd);
+        filp = fget_raw(fd);
         if (!filp)
                 goto out;
 
+        if (unlikely(filp->f_mode & FMODE_PATH)) {
+                if (!check_fcntl_cmd(cmd)) {
+                        fput(filp);
+                        goto out;
+                }
+        }
+
         err = security_file_fcntl(filp, cmd, arg);
         if (err) {
                 fput(filp);
@@ -456,10 +476,17 @@ SYSCALL_DEFINE3(fcntl64, unsigned int, fd, unsigned int, cmd,
         long err;
 
         err = -EBADF;
-        filp = fget(fd);
+        filp = fget_raw(fd);
         if (!filp)
                 goto out;
 
+        if (unlikely(filp->f_mode & FMODE_PATH)) {
+                if (!check_fcntl_cmd(cmd)) {
+                        fput(filp);
+                        goto out;
+                }
+        }
+
         err = security_file_fcntl(filp, cmd, arg);
         if (err) {
                 fput(filp);
@@ -808,14 +835,14 @@ static int __init fcntl_init(void)
          * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
          * is defined as O_NONBLOCK on some platforms and not on others.
          */
-        BUILD_BUG_ON(18 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+        BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
                 O_RDONLY        | O_WRONLY      | O_RDWR        |
                 O_CREAT         | O_EXCL        | O_NOCTTY      |
                 O_TRUNC         | O_APPEND      | /* O_NONBLOCK | */
                 __O_SYNC        | O_DSYNC       | FASYNC        |
                 O_DIRECT        | O_LARGEFILE   | O_DIRECTORY   |
                 O_NOFOLLOW      | O_NOATIME     | O_CLOEXEC     |
-                __FMODE_EXEC
+                __FMODE_EXEC    | O_PATH
                 ));
 
         fasync_cache = kmem_cache_create("fasync_cache",
diff --git a/fs/file_table.c b/fs/file_table.c
index eb36b6b17e26..3c16e1ca163e 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -276,11 +276,10 @@ struct file *fget(unsigned int fd)
         rcu_read_lock();
         file = fcheck_files(files, fd);
         if (file) {
-                if (!atomic_long_inc_not_zero(&file->f_count)) {
-                        /* File object ref couldn't be taken */
-                        rcu_read_unlock();
-                        return NULL;
-                }
+                /* File object ref couldn't be taken */
+                if (file->f_mode & FMODE_PATH ||
+                    !atomic_long_inc_not_zero(&file->f_count))
+                        file = NULL;
         }
         rcu_read_unlock();
 
@@ -289,6 +288,23 @@ struct file *fget(unsigned int fd)
 
 EXPORT_SYMBOL(fget);
 
+struct file *fget_raw(unsigned int fd)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        rcu_read_lock();
+        file = fcheck_files(files, fd);
+        if (file) {
+                /* File object ref couldn't be taken */
+                if (!atomic_long_inc_not_zero(&file->f_count))
+                        file = NULL;
+        }
+        rcu_read_unlock();
+
+        return file;
+}
+
 /*
  * Lightweight file lookup - no refcnt increment if fd table isn't shared.
  *
@@ -313,6 +329,33 @@ struct file *fget_light(unsigned int fd, int *fput_needed)
         *fput_needed = 0;
         if (atomic_read(&files->count) == 1) {
                 file = fcheck_files(files, fd);
+                if (file && (file->f_mode & FMODE_PATH))
+                        file = NULL;
+        } else {
+                rcu_read_lock();
+                file = fcheck_files(files, fd);
+                if (file) {
+                        if (!(file->f_mode & FMODE_PATH) &&
+                            atomic_long_inc_not_zero(&file->f_count))
+                                *fput_needed = 1;
+                        else
+                                /* Didn't get the reference, someone's freed */
+                                file = NULL;
+                }
+                rcu_read_unlock();
+        }
+
+        return file;
+}
+
+struct file *fget_raw_light(unsigned int fd, int *fput_needed)
+{
+        struct file *file;
+        struct files_struct *files = current->files;
+
+        *fput_needed = 0;
+        if (atomic_read(&files->count) == 1) {
+                file = fcheck_files(files, fd);
         } else {
                 rcu_read_lock();
                 file = fcheck_files(files, fd);
diff --git a/fs/namei.c b/fs/namei.c
index 33be51a2ddb7..e1d9f90d9776 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1544,7 +1544,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
         } else {
                 struct dentry *dentry;
 
-                file = fget_light(dfd, &fput_needed);
+                file = fget_raw_light(dfd, &fput_needed);
                 retval = -EBADF;
                 if (!file)
                         goto out_fail;
diff --git a/fs/open.c b/fs/open.c
index 48afc5c139d2..14a51de01f54 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -669,11 +669,16 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
                                         int (*open)(struct inode *, struct file *),
                                         const struct cred *cred)
 {
+        static const struct file_operations empty_fops = {};
         struct inode *inode;
         int error;
 
         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
                                 FMODE_PREAD | FMODE_PWRITE;
+
+        if (unlikely(f->f_flags & O_PATH))
+                f->f_mode = FMODE_PATH;
+
         inode = dentry->d_inode;
         if (f->f_mode & FMODE_WRITE) {
                 error = __get_file_write_access(inode, mnt);
@@ -687,9 +692,15 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
         f->f_path.dentry = dentry;
         f->f_path.mnt = mnt;
         f->f_pos = 0;
-        f->f_op = fops_get(inode->i_fop);
         file_sb_list_add(f, inode->i_sb);
 
+        if (unlikely(f->f_mode & FMODE_PATH)) {
+                f->f_op = &empty_fops;
+                return f;
+        }
+
+        f->f_op = fops_get(inode->i_fop);
+
         error = security_dentry_open(f, cred);
         if (error)
                 goto cleanup_all;
@@ -911,9 +922,18 @@ static inline int build_open_flags(int flags, int mode, struct open_flags *op)
         if (flags & __O_SYNC)
                 flags |= O_DSYNC;
 
-        op->open_flag = flags;
+        /*
+         * If we have O_PATH in the open flag. Then we
+         * cannot have anything other than the below set of flags
+         */
+        if (flags & O_PATH) {
+                flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
+                acc_mode = 0;
+        } else {
+                acc_mode = MAY_OPEN | ACC_MODE(flags);
+        }
 
-        acc_mode = MAY_OPEN | ACC_MODE(flags);
+        op->open_flag = flags;
 
         /* O_TRUNC implies we need access checks for write permissions */
         if (flags & O_TRUNC)
@@ -926,7 +946,8 @@ static inline int build_open_flags(int flags, int mode, struct open_flags *op)
 
         op->acc_mode = acc_mode;
 
-        op->intent = LOOKUP_OPEN;
+        op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
+
         if (flags & O_CREAT) {
                 op->intent |= LOOKUP_CREATE;
                 if (flags & O_EXCL)
@@ -1053,8 +1074,10 @@ int filp_close(struct file *filp, fl_owner_t id)
         if (filp->f_op && filp->f_op->flush)
                 retval = filp->f_op->flush(filp, id);
 
-        dnotify_flush(filp, id);
-        locks_remove_posix(filp, id);
+        if (likely(!(filp->f_mode & FMODE_PATH))) {
+                dnotify_flush(filp, id);
+                locks_remove_posix(filp, id);
+        }
         fput(filp);
         return retval;
 }
diff --git a/include/asm-generic/fcntl.h b/include/asm-generic/fcntl.h
index 0fc16e3f0bfc..84793c7025e2 100644
--- a/include/asm-generic/fcntl.h
+++ b/include/asm-generic/fcntl.h
@@ -80,6 +80,10 @@
 #define O_SYNC          (__O_SYNC|O_DSYNC)
 #endif
 
+#ifndef O_PATH
+#define O_PATH          010000000
+#endif
+
 #ifndef O_NDELAY
 #define O_NDELAY        O_NONBLOCK
 #endif
diff --git a/include/linux/file.h b/include/linux/file.h
index e85baebf6279..21a79958541c 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -29,6 +29,8 @@ static inline void fput_light(struct file *file, int fput_needed)
 
 extern struct file *fget(unsigned int fd);
 extern struct file *fget_light(unsigned int fd, int *fput_needed);
+extern struct file *fget_raw(unsigned int fd);
+extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);
 extern void set_close_on_exec(unsigned int fd, int flag);
 extern void put_filp(struct file *);
 extern int alloc_fd(unsigned start, unsigned flags);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f2143e0942c2..13df14e2c42e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -102,6 +102,9 @@ struct inodes_stat_t {
 /* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
 #define FMODE_UNSIGNED_OFFSET   ((__force fmode_t)0x2000)
 
+/* File is opened with O_PATH; almost nothing can be done with it */
+#define FMODE_PATH              ((__force fmode_t)0x4000)
+
 /* File was opened by fanotify and shouldn't generate fanotify events */
 #define FMODE_NONOTIFY          ((__force fmode_t)0x1000000)