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authorLinus Torvalds <torvalds@linux-foundation.org>2010-08-12 17:54:33 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-13 13:31:09 -0700
commit52423b90e1f5b1bdbbcc6e32f4d37ada29b790c4 (patch)
treece931c61d60aeaad2965536265c32d866d2f450b /arch
parent96fbd3f232d1c0b0c174b5804dce35f16c7eae63 (diff)
mm: keep a guard page below a grow-down stack segment
commit 320b2b8de12698082609ebbc1a17165727f4c893 upstream. 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 <keithp@keithp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
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