Re: [PATCH v3 1/6] locks: consolidate common code in theflock_to_posix_lock routines

[J. Bruce Fields]

On Wed, Dec 11, 2013 at 11:54:33AM -0500, Jeff Layton wrote:
> On Wed, 11 Dec 2013 10:19:31 -0500
> "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> 
> > On Wed, Dec 11, 2013 at 09:37:24AM -0500, J. Bruce Fields wrote:
> > > Well, it'd be weird if I didn't screw up something somewhere.
> > 
> > Yes, a classic: I forgot the breaks after each switch case.
> > 
> > Here's a version that at least doesn't return -EINVAL on every lock
> > attempt.
> > 
> > --b.
> > 
> > commit 70b7b9a442d06a71306736eb01cedba5dd6d86cf
> > Author: J. Bruce Fields <bfields@xxxxxxxxxx>
> > Date:   Tue Dec 10 18:14:28 2013 -0500
> > 
> >     locks: fix posix lock range overflow handling
> >     
> >     In the 32-bit case fcntl is converting signed 64-bit to signed 32-bit
> >     quantities in a couple places, with probably incorrect results.
> >     
> >     So instead let's return -EOVERFLOW as described in SUSv3, whenever "the
> >     smallest or, if l_len is non-zero, the largest offset of any byte in the
> >     requested segment cannot be represented correctly in an object of type
> >     off_t."
> >     
> >     While we're here, do some cleanup including consolidating code for the
> >     flock and flock64 cases.
> >     
> >     Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> > 
> > diff --git a/fs/locks.c b/fs/locks.c
> > index 92a0f0a..b70486a 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -344,48 +344,44 @@ static int assign_type(struct file_lock *fl, long type)
> >  	return 0;
> >  }
> >  
> > -/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
> > - * style lock.
> > - */
> > -static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
> > -			       struct flock *l)
> > +static int flock_to_posix_lock_common(struct file *filp, struct file_lock *fl,
> > +					struct flock64 *l, loff_t offset_max)
> >  {
> > -	off_t start, end;
> > +	loff_t start;
> >  
> >  	switch (l->l_whence) {
> >  	case SEEK_SET:
> > -		start = 0;
> > +		fl->fl_start = 0;
> >  		break;
> >  	case SEEK_CUR:
> > -		start = filp->f_pos;
> > +		fl->fl_start = filp->f_pos;
> >  		break;
> >  	case SEEK_END:
> > -		start = i_size_read(file_inode(filp));
> > +		fl->fl_start = i_size_read(file_inode(filp));
> >  		break;
> >  	default:
> >  		return -EINVAL;
> >  	}
> > +	if (l->l_start < 0)
> > +		return -EINVAL;
> > +	if (l->l_start > offset_max - fl->fl_start)
> > +		return -EOVERFLOW;
> > +	fl->fl_start += l->l_start;
> > +	if (l->l_len > offset_max - fl->fl_start)
> > +		return -EOVERFLOW;
> > +	if (fl->fl_start + l->l_len < 0)
> > +		return -EINVAL;
> >  
> >  	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
> >  	   POSIX-2001 defines it. */
> > -	start += l->l_start;
> > -	if (start < 0)
> > -		return -EINVAL;
> > -	fl->fl_end = OFFSET_MAX;
> > -	if (l->l_len > 0) {
> > -		end = start + l->l_len - 1;
> > -		fl->fl_end = end;
> > -	} else if (l->l_len < 0) {
> > -		end = start - 1;
> > -		fl->fl_end = end;
> > -		start += l->l_len;
> > -		if (start < 0)
> > -			return -EINVAL;
> > -	}
> > -	fl->fl_start = start;	/* we record the absolute position */
> > -	if (fl->fl_end < fl->fl_start)
> > -		return -EOVERFLOW;
> > -	
> > +	if (l->l_len > 0)
> > +		fl->fl_end = fl->fl_start + l->l_len - 1;
> > +	else if (l->l_len < 0) {
> > +		fl->fl_end = start - 1;
> > +		fl->fl_start += l->l_len;
> > +	} else
> > +		fl->fl_end = OFFSET_MAX;
> > +
> >  	fl->fl_owner = current->files;
> >  	fl->fl_pid = current->tgid;
> >  	fl->fl_file = filp;
> > @@ -396,50 +392,27 @@ static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
> >  	return assign_type(fl, l->l_type);
> >  }
> >  
> > +/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
> > + * style lock.
> > + */
> > +static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
> > +			       struct flock *l)
> > +{
> > +	struct flock64 ll = {
> > +		.l_type = l->l_type,
> > +		.l_whence = l->l_whence,
> > +		.l_start = l->l_start,
> > +		.l_len = l->l_len,
> > +	};
> > +	
> > +	return flock_to_posix_lock_common(filp, fl, &ll, OFFT_OFFSET_MAX);
> > +}
> > +
> >  #if BITS_PER_LONG == 32
> >  static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
> >  				 struct flock64 *l)
> >  {
> > -	loff_t start;
> > -
> > -	switch (l->l_whence) {
> > -	case SEEK_SET:
> > -		start = 0;
> > -		break;
> > -	case SEEK_CUR:
> > -		start = filp->f_pos;
> > -		break;
> > -	case SEEK_END:
> > -		start = i_size_read(file_inode(filp));
> > -		break;
> > -	default:
> > -		return -EINVAL;
> > -	}
> > -
> > -	start += l->l_start;
> > -	if (start < 0)
> > -		return -EINVAL;
> > -	fl->fl_end = OFFSET_MAX;
> > -	if (l->l_len > 0) {
> > -		fl->fl_end = start + l->l_len - 1;
> > -	} else if (l->l_len < 0) {
> > -		fl->fl_end = start - 1;
> > -		start += l->l_len;
> > -		if (start < 0)
> > -			return -EINVAL;
> > -	}
> > -	fl->fl_start = start;	/* we record the absolute position */
> > -	if (fl->fl_end < fl->fl_start)
> > -		return -EOVERFLOW;
> > -	
> > -	fl->fl_owner = current->files;
> > -	fl->fl_pid = current->tgid;
> > -	fl->fl_file = filp;
> > -	fl->fl_flags = FL_POSIX;
> > -	fl->fl_ops = NULL;
> > -	fl->fl_lmops = NULL;
> > -
> > -	return assign_type(fl, l->l_type);
> > +	return flock_to_posix_lock_common(filp, fl, l, OFFSET_MAX);
> >  }
> >  #endif
> >  
> > diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
> > index 95e46c8..36025f7 100644
> > --- a/include/uapi/asm-generic/fcntl.h
> > +++ b/include/uapi/asm-generic/fcntl.h
> > @@ -186,8 +186,6 @@ struct flock {
> >  };
> >  #endif
> >  
> > -#ifndef CONFIG_64BIT
> > -
> >  #ifndef HAVE_ARCH_STRUCT_FLOCK64
> >  #ifndef __ARCH_FLOCK64_PAD
> >  #define __ARCH_FLOCK64_PAD
> > @@ -202,6 +200,5 @@ struct flock64 {
> >  	__ARCH_FLOCK64_PAD
> >  };
> >  #endif
> > -#endif /* !CONFIG_64BIT */
> >  
> >  #endif /* _ASM_GENERIC_FCNTL_H */
> 
> Thanks -- looks like this is hitting the same discrepancy that I was
> getting with my consolidation attempt. Setting a lock like this on
> x86_64 fails with the current kernel:
> 
> 	struct flock lck1 = {
> 		.l_type		= F_WRLCK,
> 		.l_whence	= SEEK_SET,
> 		.l_start	= 0,
> 		.l_len		= LONG_MAX,
> 	};

Are you sure?  I've tried but can't reproduce that.  I'm on 3.13-rc3
plus a couple DRC patches from you.

--b.

> 
> 
> ...but succeeds with your patch in place. I've not sat down yet to
> figure out whether you broke or fixed something though :).
> 
> -- 
> Jeff Layton <jlayton@xxxxxxxxxx>
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