Date: Tue, 2 Feb 1999 11:39:01 -0500 (EST) From: Robert Watson <robert@cyrus.watson.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: current@FreeBSD.ORG Subject: Re: swap_page_getswapspace failed (don't do stupid things with /dev/mem) Message-ID: <Pine.BSF.3.96.990202113636.13771B-100000@fledge.watson.org> In-Reply-To: <199902020434.UAA31836@apollo.backplane.com>
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On Mon, 1 Feb 1999, Matthew Dillon wrote: > :So this probably works for non-root users on files like /dev/zero that can > :produce as much data as you might be interested in, suggesting a fun > :denial of service attack for the bored and/or insane. > > Presumably the datasize limit can be used restrict the size > of the process. Matt, Does datasize limit the number of backed pages, or the amount of address space used by a process? I.e., can I grow myself a large chunk of address space using mmap to the same region of a file, and then read into that large chunk (presumably larger than the cache size if I want to be nasty)? If datasize only affects backed pages, then we can still do nasty large copies; if it affects address space, then nasty large copies are limited to the size of the writable address space (if using readv) or the size of the largest contiguous writable space (if using read). Robert N Watson robert@fledge.watson.org http://www.watson.org/~robert/ PGP key fingerprint: 03 01 DD 8E 15 67 48 73 25 6D 10 FC EC 68 C1 1C Carnegie Mellon University http://www.cmu.edu/ TIS Labs at Network Associates, Inc. http://www.tis.com/ SafePort Network Services http://www.safeport.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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