releases/3.14.36/procfs-fix-race-between-symlink-removals-and-traversals.patch

   1 From 7e0e953bb0cf649f93277ac8fb67ecbb7f7b04a9 Mon Sep 17 00:00:00 2001
   2 From: Al Viro <viro@zeniv.linux.org.uk>
   3 Date: Sat, 21 Feb 2015 22:16:11 -0500
   4 Subject: procfs: fix race between symlink removals and traversals
   5
   6 From: Al Viro <viro@zeniv.linux.org.uk>
   7
   8 commit 7e0e953bb0cf649f93277ac8fb67ecbb7f7b04a9 upstream.
   9
  10 use_pde()/unuse_pde() in ->follow_link()/->put_link() resp.
  11
  12 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
  13 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  14
  15 ---
  16  fs/proc/generic.c  |   12 ------------
  17  fs/proc/inode.c    |   21 +++++++++++++++++++++
  18  fs/proc/internal.h |    1 +
  19  3 files changed, 22 insertions(+), 12 deletions(-)
  20
  21 --- a/fs/proc/generic.c
  22 +++ b/fs/proc/generic.c
  23 @@ -19,7 +19,6 @@
  24  #include <linux/mount.h>
  25  #include <linux/init.h>
  26  #include <linux/idr.h>
  27 -#include <linux/namei.h>
  28  #include <linux/bitops.h>
  29  #include <linux/spinlock.h>
  30  #include <linux/completion.h>
  31 @@ -162,17 +161,6 @@ void proc_free_inum(unsigned int inum)
  32         spin_unlock_irqrestore(&proc_inum_lock, flags);
  33  }
  34
  35 -static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
  36 -{
  37 -       nd_set_link(nd, __PDE_DATA(dentry->d_inode));
  38 -       return NULL;
  39 -}
  40 -
  41 -static const struct inode_operations proc_link_inode_operations = {
  42 -       .readlink       = generic_readlink,
  43 -       .follow_link    = proc_follow_link,
  44 -};
  45 -
  46  /*
  47   * Don't create negative dentries here, return -ENOENT by hand
  48   * instead.
  49 --- a/fs/proc/inode.c
  50 +++ b/fs/proc/inode.c
  51 @@ -23,6 +23,7 @@
  52  #include <linux/slab.h>
  53  #include <linux/mount.h>
  54  #include <linux/magic.h>
  55 +#include <linux/namei.h>
  56
  57  #include <asm/uaccess.h>
  58
  59 @@ -401,6 +402,26 @@ static const struct file_operations proc
  60  };
  61  #endif
  62
  63 +static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
  64 +{
  65 +       struct proc_dir_entry *pde = PDE(dentry->d_inode);
  66 +       if (unlikely(!use_pde(pde)))
  67 +               return ERR_PTR(-EINVAL);
  68 +       nd_set_link(nd, pde->data);
  69 +       return pde;
  70 +}
  71 +
  72 +static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
  73 +{
  74 +       unuse_pde(p);
  75 +}
  76 +
  77 +const struct inode_operations proc_link_inode_operations = {
  78 +       .readlink       = generic_readlink,
  79 +       .follow_link    = proc_follow_link,
  80 +       .put_link       = proc_put_link,
  81 +};
  82 +
  83  struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
  84  {
  85         struct inode *inode = new_inode_pseudo(sb);
  86 --- a/fs/proc/internal.h
  87 +++ b/fs/proc/internal.h
  88 @@ -202,6 +202,7 @@ struct pde_opener {
  89         int closing;
  90         struct completion *c;
  91  };
  92 +extern const struct inode_operations proc_link_inode_operations;
  93
  94  extern const struct inode_operations proc_pid_link_inode_operations;
  95