Hi,
> Shhh ;-) Last time that hack was mentioned, someone wanted to _remove_
> it. It's a very nice little hack to have around, and IKD uses it.
I am not saying it should be removed. But IMO it is a legitimate (if
not the originally intended) use of "start" to serve as a pointer to
a memory area allocated in the proc_read () function. This use is broken
with this hack in its current form, because reading from such a file
will fail depending on the (random) order of the page and start pointers.
If I understand the "hack" right, legitimate offsets generated for it
are always between 0 and PAGE_SIZE. Therefore the patch below would
not break it, while overcoming the abovementioned problem, because
legitimate page pointers will never be < PAGE_SIZE.
Please correct me if I'm wrong.
Cheers,
Martin
--
Martin Wilck <[EMAIL PROTECTED]>
FSC EP PS DS1, Paderborn Tel. +49 5251 8 15113
--- linux-2.4.5/fs/proc/generic.c Mon Jun 25 13:46:26 2001
+++ 2.4.5mw/fs/proc/generic.c Tue Jun 26 20:42:22 2001
@@ -104,14 +104,14 @@
* return the bytes, and set `start' to the desired offset
* as an unsigned int. - [EMAIL PROTECTED]
*/
- n -= copy_to_user(buf, start < page ? page : start, n);
+ n -= copy_to_user(buf, (unsigned long) start < PAGE_SIZE ? page :
+start, n);
if (n == 0) {
if (retval == 0)
retval = -EFAULT;
break;
}
- *ppos += start < page ? (long)start : n; /* Move down the file */
+ *ppos += (unsigned long) start < PAGE_SIZE ? (unsigned long) start :
+n; /* Move down the file */
nbytes -= n;
buf += n;
retval += n;
-
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