Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs fixes from Al Viro:
 "stable fodder; assorted deadlock fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vt: synchronize_rcu() under spinlock is not nice...
  Nest rename_lock inside vfsmount_lock
  Don't bother with redoing rw_verify_area() from default_file_splice_from()

5 files changed, 48 insertions, 8 deletions

diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index e4ca345873c3..d7799deacb21 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -93,7 +93,7 @@ vcs_poll_data_free(struct vcs_poll_data *poll)
 static struct vcs_poll_data *
 vcs_poll_data_get(struct file *file)
 {
-        struct vcs_poll_data *poll = file->private_data;
+        struct vcs_poll_data *poll = file->private_data, *kill = NULL;
 
         if (poll)
                 return poll;
@@ -122,10 +122,12 @@ vcs_poll_data_get(struct file *file)
                 file->private_data = poll;
         } else {
                 /* someone else raced ahead of us */
-                vcs_poll_data_free(poll);
+                kill = poll;
                 poll = file->private_data;
         }
         spin_unlock(&file->f_lock);
+        if (kill)
+                vcs_poll_data_free(kill);
 
         return poll;
 }
diff --git a/fs/dcache.c b/fs/dcache.c
index fbfae008ba44..e8bc3420d63e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2542,7 +2542,6 @@ static int prepend_path(const struct path *path,
         bool slash = false;
         int error = 0;
 
-        br_read_lock(&vfsmount_lock);
         while (dentry != root->dentry || vfsmnt != root->mnt) {
                 struct dentry * parent;
 
@@ -2572,8 +2571,6 @@ static int prepend_path(const struct path *path,
         if (!error && !slash)
                 error = prepend(buffer, buflen, "/", 1);
 
-out:
-        br_read_unlock(&vfsmount_lock);
         return error;
 
 global_root:
@@ -2590,7 +2587,7 @@ global_root:
                 error = prepend(buffer, buflen, "/", 1);
         if (!error)
                 error = is_mounted(vfsmnt) ? 1 : 2;
-        goto out;
+        return error;
 }
 
 /**
@@ -2617,9 +2614,11 @@ char *__d_path(const struct path *path,
         int error;
 
         prepend(&res, &buflen, "\0", 1);
+        br_read_lock(&vfsmount_lock);
         write_seqlock(&rename_lock);
         error = prepend_path(path, root, &res, &buflen);
         write_sequnlock(&rename_lock);
+        br_read_unlock(&vfsmount_lock);
 
         if (error < 0)
                 return ERR_PTR(error);
@@ -2636,9 +2635,11 @@ char *d_absolute_path(const struct path *path,
         int error;
 
         prepend(&res, &buflen, "\0", 1);
+        br_read_lock(&vfsmount_lock);
         write_seqlock(&rename_lock);
         error = prepend_path(path, &root, &res, &buflen);
         write_sequnlock(&rename_lock);
+        br_read_unlock(&vfsmount_lock);
 
         if (error > 1)
                 error = -EINVAL;
@@ -2702,11 +2703,13 @@ char *d_path(const struct path *path, char *buf, int buflen)
                 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
 
         get_fs_root(current->fs, &root);
+        br_read_lock(&vfsmount_lock);
         write_seqlock(&rename_lock);
         error = path_with_deleted(path, &root, &res, &buflen);
+        write_sequnlock(&rename_lock);
+        br_read_unlock(&vfsmount_lock);
         if (error < 0)
                 res = ERR_PTR(error);
-        write_sequnlock(&rename_lock);
         path_put(&root);
         return res;
 }
@@ -2830,6 +2833,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
         get_fs_root_and_pwd(current->fs, &root, &pwd);
 
         error = -ENOENT;
+        br_read_lock(&vfsmount_lock);
         write_seqlock(&rename_lock);
         if (!d_unlinked(pwd.dentry)) {
                 unsigned long len;
@@ -2839,6 +2843,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
                 prepend(&cwd, &buflen, "\0", 1);
                 error = prepend_path(&pwd, &root, &cwd, &buflen);
                 write_sequnlock(&rename_lock);
+                br_read_unlock(&vfsmount_lock);
 
                 if (error < 0)
                         goto out;
@@ -2859,6 +2864,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
                 }
         } else {
                 write_sequnlock(&rename_lock);
+                br_read_unlock(&vfsmount_lock);
         }
 
 out:
diff --git a/fs/internal.h b/fs/internal.h
index 507141fceb99..4be78237d896 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -125,3 +125,8 @@ extern int invalidate_inodes(struct super_block *, bool);
  * dcache.c
  */
 extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
+
+/*
+ * read_write.c
+ */
+extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
diff --git a/fs/read_write.c b/fs/read_write.c
index a698eff457fb..f7b5a23b804b 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -17,6 +17,7 @@
 #include <linux/splice.h>
 #include <linux/compat.h>
 #include "read_write.h"
+#include "internal.h"
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -417,6 +418,30 @@ ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, lof
 
 EXPORT_SYMBOL(do_sync_write);
 
+ssize_t __kernel_write(struct file *file, const char *buf, size_t count, loff_t *pos)
+{
+        mm_segment_t old_fs;
+        const char __user *p;
+        ssize_t ret;
+
+        old_fs = get_fs();
+        set_fs(get_ds());
+        p = (__force const char __user *)buf;
+        if (count > MAX_RW_COUNT)
+                count =  MAX_RW_COUNT;
+        if (file->f_op->write)
+                ret = file->f_op->write(file, p, count, pos);
+        else
+                ret = do_sync_write(file, p, count, pos);
+        set_fs(old_fs);
+        if (ret > 0) {
+                fsnotify_modify(file);
+                add_wchar(current, ret);