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Message-ID: <20131211165918.GE29300@fieldses.org>
Date: Wed, 11 Dec 2013 11:59:18 -0500
From: "J. Bruce Fields" <bfields@...ldses.org>
To: Jeff Layton <jlayton@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
nfs-ganesha-devel@...ts.sourceforge.net,
samba-technical@...ts.samba.org
Subject: Re: [PATCH v3 1/6] locks: consolidate common code in the
flock_to_posix_lock routines
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@...ldses.org> 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@...hat.com>
> > 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@...hat.com>
> >
> > 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@...hat.com>
--
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