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SubjectRe: lseek/llseek allows the negative offset
On Sat, Nov 18, 2000 at 07:25:42PM +0100, Andrea Arcangeli wrote:
> On Fri, Nov 17, 2000 at 04:09:00PM -0800, H . J . Lu wrote:
> > On Fri, Nov 17, 2000 at 03:59:13PM -0800, H . J . Lu wrote:
> > > # gcc x.c
> > > # ./a.out
> > > lseek on -100000: -100000
> > > write: File too large
> > >
> > > Should kernel allow negative offsets for lseek/llseek?
> > >
> > >
> >
> > Never mind. I was running the wrong kernel.
>
> With 2.2.18pre21aa2 this little proggy:
>
> main()
> {
> int fd = creat("x", 0600);
> lseek(fd, 0x80000000, 0);
> }
>
> get confused this way:
>
> lseek(3, 2147483648, SEEK_SET) = -1 ERRNO_0 (Success)
> _exit(-2147483648) = ?
>
> I fixed it this way:
>
> diff -urN 2.2.18pre21/fs/read_write.c lseek/fs/read_write.c
> --- 2.2.18pre21/fs/read_write.c Tue Sep 5 02:28:49 2000
> +++ lseek/fs/read_write.c Sat Nov 18 18:42:55 2000
> @@ -53,6 +53,10 @@
> struct dentry * dentry;
> struct inode * inode;
>
> + retval = -EINVAL;
> + if (offset < 0)
> + goto out_nolock;
> +

offset shouldn't be < 0 to begin with. There may be a bug somewhere
else. In my case,

if (offset < 0)
return -EINVAL;

is missing from those FS lseek functions.

H.J.

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