On Mon, Feb 06, 2012 at 06:05:30PM -0600, Josh Hunt wrote:
> We've hit an issue where our 32-bit applications, when running on a
> 64-bit kernel, using poll() and passing in a value of -1 for the timeout
> return after ~49 days (2^32 msec). Instead of waiting indefinitely as it
> is stated they should. Reproducing the issue is trivial. I've
> instrumented the kernel and found we are hitting the case where poll()
> believes we've passed in a positive number and thus creates a timespec,
> etc. Currently poll() is defined in userspace as:
>
> int poll(struct pollfd *ufds, nfds_t nfds, int timeout);
>
> but in the kernel timeout is of type long.
>
> I can think of a few ways to solve this. One, which is the patch I've
> attached, is to change the type of timeout to int in the kernel. I'm not
> certain the ramifications this may have since it's changing a syscall's
> arguments which may be a big no-no :) Another way I am proposing is by
> bounds checking. Currently we do the following:
>
> if (timeout_msecs >= 0) {
> to = &end_time;
> poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
> NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
> }
>
> We could add an upper bound on timeout_msecs to say < 0xffffffff. I'm
> not sure if either is acceptable though.
Or just add compat_sys_poll() with that argument being int and have it call
sys_poll(). The value will be sign-extended...
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
