Commit 9419a319 authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAmir Goldstein <amir73il@gmail.com>
Reported-by: default avatar <syzbot+2a73a6ea9507b7112141@syzkaller.appspotmail.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 79a3aaa7

fs/internal.h

+0 −2
Original line number Diff line number Diff line
@@ -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 *);



/*

include/linux/mount.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/acct.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}

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