From: Linus Torvalds Date: Fri, 13 Aug 2010 00:54:33 +0000 (-0700) Subject: mm: keep a guard page below a grow-down stack segment X-Git-Tag: v2.6.36-rc1~48 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=320b2b8de12698082609ebbc1a17165727f4c893;p=pandora-kernel.git mm: keep a guard page below a grow-down stack segment This is a rather minimally invasive patch to solve the problem of the user stack growing into a memory mapped area below it. Whenever we fill the first page of the stack segment, expand the segment down by one page. Now, admittedly some odd application might _want_ the stack to grow down into the preceding memory mapping, and so we may at some point need to make this a process tunable (some people might also want to have more than a single page of guarding), but let's try the minimal approach first. Tested with trivial application that maps a single page just below the stack, and then starts recursing. Without this, we will get a SIGSEGV _after_ the stack has smashed the mapping. With this patch, we'll get a nice SIGBUS just as the stack touches the page just above the mapping. Requested-by: Keith Packard Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed