acct_on(): don't mess with freeze protection
What happens there is that we are replacing file->path.mnt of
a file we'd just opened with a clone and we need the write
count contribution to be transferred from original mount to
new one. That's it. We do *NOT* want any kind of freeze
protection for the duration of switchover.
IOW, we should just use __mnt_{want,drop}_write() for that
switchover; no need to bother with mnt_{want,drop}_write()
there.
Tested-by: Amir Goldstein <amir73il@gmail.com>
Reported-by: syzbot+2a73a6ea9507b7112141@syzkaller.appspotmail.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/internal.h b/fs/internal.h
index 6a8b716..2e73628 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -89,9 +89,7 @@ extern int sb_prepare_remount_readonly(struct super_block *);
extern void __init mnt_init(void);
-extern int __mnt_want_write(struct vfsmount *);
extern int __mnt_want_write_file(struct file *);
-extern void __mnt_drop_write(struct vfsmount *);
extern void __mnt_drop_write_file(struct file *);
/*
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 9197ddb..bf8cc41 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -87,6 +87,8 @@ extern bool mnt_may_suid(struct vfsmount *mnt);
struct path;
extern struct vfsmount *clone_private_mount(const struct path *path);
+extern int __mnt_want_write(struct vfsmount *);
+extern void __mnt_drop_write(struct vfsmount *);
struct file_system_type;
extern struct vfsmount *fc_mount(struct fs_context *fc);
diff --git a/kernel/acct.c b/kernel/acct.c
index addf773..81f9831 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -227,7 +227,7 @@ static int acct_on(struct filename *pathname)
filp_close(file, NULL);
return PTR_ERR(internal);
}
- err = mnt_want_write(internal);
+ err = __mnt_want_write(internal);
if (err) {
mntput(internal);
kfree(acct);
@@ -252,7 +252,7 @@ static int acct_on(struct filename *pathname)
old = xchg(&ns->bacct, &acct->pin);
mutex_unlock(&acct->lock);
pin_kill(old);
- mnt_drop_write(mnt);
+ __mnt_drop_write(mnt);
mntput(mnt);
return 0;
}