queue-5.0/acct_on-don-t-mess-with-freeze-protection.patch

   1 From 9419a3191dcb27f24478d288abaab697228d28e6 Mon Sep 17 00:00:00 2001
   2 From: Al Viro <viro@zeniv.linux.org.uk>
   3 Date: Thu, 4 Apr 2019 21:04:13 -0400
   4 Subject: acct_on(): don't mess with freeze protection
   5
   6 From: Al Viro <viro@zeniv.linux.org.uk>
   7
   8 commit 9419a3191dcb27f24478d288abaab697228d28e6 upstream.
   9
  10 What happens there is that we are replacing file->path.mnt of
  11 a file we'd just opened with a clone and we need the write
  12 count contribution to be transferred from original mount to
  13 new one.  That's it.  We do *NOT* want any kind of freeze
  14 protection for the duration of switchover.
  15
  16 IOW, we should just use __mnt_{want,drop}_write() for that
  17 switchover; no need to bother with mnt_{want,drop}_write()
  18 there.
  19
  20 Tested-by: Amir Goldstein <amir73il@gmail.com>
  21 Reported-by: syzbot+2a73a6ea9507b7112141@syzkaller.appspotmail.com
  22 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
  23 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  24
  25 ---
  26  fs/internal.h         |    2 --
  27  include/linux/mount.h |    2 ++
  28  kernel/acct.c         |    4 ++--
  29  3 files changed, 4 insertions(+), 4 deletions(-)
  30
  31 --- a/fs/internal.h
  32 +++ b/fs/internal.h
  33 @@ -80,9 +80,7 @@ extern int sb_prepare_remount_readonly(s
  34
  35  extern void __init mnt_init(void);
  36
  37 -extern int __mnt_want_write(struct vfsmount *);
  38  extern int __mnt_want_write_file(struct file *);
  39 -extern void __mnt_drop_write(struct vfsmount *);
  40  extern void __mnt_drop_write_file(struct file *);
  41
  42  /*
  43 --- a/include/linux/mount.h
  44 +++ b/include/linux/mount.h
  45 @@ -86,6 +86,8 @@ extern bool mnt_may_suid(struct vfsmount
  46
  47  struct path;
  48  extern struct vfsmount *clone_private_mount(const struct path *path);
  49 +extern int __mnt_want_write(struct vfsmount *);
  50 +extern void __mnt_drop_write(struct vfsmount *);
  51
  52  struct file_system_type;
  53  extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
  54 --- a/kernel/acct.c
  55 +++ b/kernel/acct.c
  56 @@ -227,7 +227,7 @@ static int acct_on(struct filename *path
  57                 filp_close(file, NULL);
  58                 return PTR_ERR(internal);
  59         }
  60 -       err = mnt_want_write(internal);
  61 +       err = __mnt_want_write(internal);
  62         if (err) {
  63                 mntput(internal);
  64                 kfree(acct);
  65 @@ -252,7 +252,7 @@ static int acct_on(struct filename *path
  66         old = xchg(&ns->bacct, &acct->pin);
  67         mutex_unlock(&acct->lock);
  68         pin_kill(old);
  69 -       mnt_drop_write(mnt);
  70 +       __mnt_drop_write(mnt);
  71         mntput(mnt);
  72         return 0;
  73  }