[PATCH v3 1/6] locks: consolidate common code in the flock_to_posix_lock routines
Jeff Layton
jlayton at redhat.com
Wed Dec 11 11:09:01 MST 2013
On Wed, 11 Dec 2013 11:59:18 -0500
"J. Bruce Fields" <bfields at fieldses.org> wrote:
> 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 at fieldses.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 at redhat.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 at redhat.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.
>
Nope, my bad -- stupid mistake on my part. My test program had F_WRLCKP,
which of course *should* get an EINVAL on the older kernel. Patch seems
to be fine so far in all of the edge cases I've tested (which
admittedly, isn't many).
--
Jeff Layton <jlayton at redhat.com>
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