Messages in this thread | | | From | Sasha Levin <> | Date | Fri, 30 Mar 2012 20:15:00 +0300 | Subject | Re: [PATCH] kmsg: Use vmalloc instead of kmalloc when writing |
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On Fri, Mar 30, 2012 at 7:49 PM, Greg KH <gregkh@linuxfoundation.org> wrote: > On Fri, Mar 30, 2012 at 07:37:37PM +0300, Sasha Levin wrote: >> On Fri, Mar 30, 2012 at 6:30 PM, Greg KH <gregkh@linuxfoundation.org> wrote: >> > On Fri, Mar 30, 2012 at 01:04:27PM -0400, Sasha Levin wrote: >> >> There are no size checks in kmsg_write(), and we try allocating enough >> >> memory to store everything userspace gave us, which may be too much for >> >> kmalloc to allocate. >> > >> > Really? Have you seen this fail? As only root can do this, is this >> > really a problem? >> >> Only root, and a whole bunch of management software that dumps data >> into /dev/kmsg (systemd and friends). > > Running as root, do any of these cause problems by asking for too much > memory here? Is this something that needs to be addressed now, and in > stable kernels, or can it wait for 3.5?
The only harm there is a kernel warning and the failure to write that specific message to kmsg, combined with the fact that no one complained about it before me I think it can probably wait for 3.5.
>> >> One option would be to limit it to something, but we can't come up with >> >> a number that would make sense. >> >> >> >> Instead, just use vmalloc so that nothing would break with large amounts >> >> of data. >> > >> > Are you sure this will work properly? Have you tested it with large >> > amounts of data? >> >> My test was dumping 800mb of data into it, if there's anything else I >> should try please let me know. > > Did that fail before and now it works properly?
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