On Wed, 5 Jul 2006 20:00:34 -0700 (PDT)
Vadim Lobanov <[email protected]> wrote:
> Hi,
>
> This is a trivial patch to fix the nfds check in the poll system call
> implementation. Namely, OPEN_MAX no longer does anything important in
> the kernel, and checking that nfds is greater than max_fdset AND greater
> than OPEN_MAX therefore just seems wrong.
>
> This brings up a slightly-tangential question: Why do the nfds checks
> exist in select()/poll()? They're not strictly necessary, since bad
> input will be caught later when we validate all the fds, one by one.
> Furthermore, these checks optimize the handling of error cases (which
> should be uncommon) while pessimizing correct usage of the syscalls
> (which should be more common).
>
> Signed-off-by: Vadim Lobanov <[email protected]>
>
> diff -Npru linux-2.6.17-git25/fs/select.c linux-new/fs/select.c
> --- linux-2.6.17-git25/fs/select.c 2006-07-05 19:06:56.000000000 -0700
> +++ linux-new/fs/select.c 2006-07-05 19:10:51.000000000 -0700
> @@ -671,7 +671,7 @@ int do_sys_poll(struct pollfd __user *uf
> fdt = files_fdtable(current->files);
> max_fdset = fdt->max_fdset;
> rcu_read_unlock();
> - if (nfds > max_fdset && nfds > OPEN_MAX)
> + if (nfds > max_fdset)
> return -EINVAL;
>
> poll_initwait(&table);
http://www.opengroup.org/onlinepubs/009695399/functions/poll.html sayeth
[EINVAL]
The nfds argument is greater than {OPEN_MAX}, or ...
and afaict, max_fdset can be either less than or greater than OPEN_MAX,
depending upon how one sets NR_OPEN.
So I think that patch should be s/&&/||/ and s/changelog/new one/
If anything we do here alters userspace-visible behaviour (and it probably will)
then it should be *exahustively* documented in the changelog, and probably dropped.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
