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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>
hifive-unleashed-5.2
Al Viro 2019-04-04 21:04:13 -04:00
parent 79a3aaa7b8
commit 9419a3191d
3 changed files with 4 additions and 4 deletions
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2
fs/internal.h
View File

@ -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 *);
/*

2
include/linux/mount.h
View File

@ -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);

4
kernel/acct.c
View File

@ -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;
}