On Tue, 10 Dec 2013 18:22:04 -0500
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> On Tue, Dec 10, 2013 at 04:22:53PM -0500, bfields wrote:
> > On Tue, Dec 10, 2013 at 02:17:30PM -0500, Jeff Layton wrote:
> > > Currently, there's a lot of copy and paste between the two. Add some
> > > functions to do the initialization of the file_lock from values
> > > passed in, and turn the flock/flock64 variants of those functions into
> > > wrappers around them.
> > >
> > > Unfortunately it's harder to consolidate the fl_start/fl_end
> > > calculations due to the differently sized types involved so I've left
> > > them separate for now.
> >
> > I'd think you could assign everything to the flock64 type and do the
> > common work there or something.
> >
> > But I'm confused about what the current code is actually trying to do:
> > if I'm chasing down the definitions right, these quantities are all
> > signed, and when start is defined as an off_t it can overflow in the
> > SEEK_CUR and SEEK_END cases. And
> >
> > if (fl->fl_end < fl->fl_start)
> > return -EOVERFLOW
> >
> > is counting on overlow wrapping around, which I thought wasn't
> > guaranteed in the case of signed arithmetic?
>
> E.g. the following (untested) removes the duplication and should return
> -EOVERFLOW in the cases we currently do a random conversion from 64- to
> 32-bit and back. Susv3 says:
>
> [EOVERFLOW]
> The cmd argument is F_GETLK, F_SETLK, or F_SETLKW and 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.
>
> so that's what I tried to do.
>
> --b.
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 92a0f0a..47832f5 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -344,48 +344,41 @@ 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;
> - break;
> + fl->fl_start = 0;
> case SEEK_CUR:
> - start = filp->f_pos;
> - break;
> + fl->fl_start = filp->f_pos;
> case SEEK_END:
> - start = i_size_read(file_inode(filp));
> - break;
> + fl->fl_start = i_size_read(file_inode(filp));
> 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 +389,27 @@ 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 */
Nice. I had started to consolidate them, but then figured out that
there are so many edge cases and I didn't have a good way to test them
all.
As far as I can tell though, this looks correct. I'll plan to drop my
patch and base the rest of the set on top of yours.
Thanks,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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