Messages in this thread | | | Date | Tue, 7 Mar 2006 21:23:02 -0800 | From | Greg KH <> | Subject | Re: Fw: Re: oops in choose_configuration() |
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On Tue, Mar 07, 2006 at 10:22:10PM -0500, Dmitry Torokhov wrote: > On Tuesday 07 March 2006 20:27, Greg KH wrote: > > On Tue, Mar 07, 2006 at 08:13:28PM -0500, Dmitry Torokhov wrote: > > > On Tuesday 07 March 2006 19:57, Linus Torvalds wrote: > > > > > > > > On Tue, 7 Mar 2006, Chuck Ebbert wrote: > > > > > > > > > > At least one susbsystem rolls its own method of adding env vars to the > > > > > uevent buffer, and it's so broken it triggers the WARN_ON() in > > > > > lib/vsprintf.c::vsnprintf() by passing a negative length to that function. > > > > > > > > Well, snprintf() should be safe, though. It will warn if the caller is > > > > lazy, but these days, the thing does > > > > > > > > max(buf_size - len, 0) > > > > > > > > which should mean that the input layer passes in 0 instead of a negative > > > > number. And snprintf() will then _not_ print anything. > > > > > > > > So I think input_add_uevent_bm_var() is safe, even if it's not pretty. > > > > > > > > However, input_devices_read() doesn't do any sanity checking at all, and > > > > if that ever ends up printing more than a page, that would be bad. I > > > > didn't look very closely, but it looks worrisome. > > > > > > > > Dmitry? > > > > > > I had all this code converted to seq_file, but it depends on converting > > > input handlers to class interfaces and it is not possible nowadays > > > because with latest Greg's changes to class code we would try to > > > register class devices while registering class devices/interfaces > > > (psmouse creates input_dev which binds to mousedev interface which in > > > turn tries to create mouseX which is also belongs to input class) and > > > deadlocking. Greg promised current implementation is only a temporary > > > solution. > > > > > > I suppose I could separate those changes... > > > > That would probably be a good idea :) > > > > Hmm, what is the policy for attr->show()? With hotplug variables we > return -ENOMEM if there is not enough memory to store all data, but > what about attributes? Should we also return error (and which one, > -ENOMEM, -ENOBUFS?) or fill as much as we can and return up to > PAGE_SIZE?
Remember, sysfs files are supposed to be small, you are an "oddity" in that you have a much larger buffer that you can return due to the wierd aliases you have.
Truncating the buffer is probably good as we want userspace to get some information, right?
> With sysfs not kernel nor application can really recover > if attribute needs buffer larger than a page. Or just rely on BUG_ON > in fs/sysfs/file.c::fill_read_buffer()?
How about just making this a binary attribute, then you can handle an arbitrary size buffer and don't have to worry about the PAGE_SIZE stuff (but it makes it more code that you have to write to handle it all, there are tradeoffs...)
thanks,
greg k-h - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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