Re: [PATCH] kmsg: Use vmalloc instead of kmalloc when writing

From: Sasha Levin
Date: Fri Mar 30 2012 - 12:38:02 EST

On Fri, Mar 30, 2012 at 6:30 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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).

>> 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.

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