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authorLinus Torvalds <torvalds@linux-foundation.org>2010-08-13 02:54:33 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-13 02:54:33 +0200
commit320b2b8de12698082609ebbc1a17165727f4c893 (patch)
treebb62fe1ba3bb8bf68ff1fd44e613ece9c9581c36 /include/asm-generic
parentRevert "fsnotify: store struct file not struct path" (diff)
downloadlinux-320b2b8de12698082609ebbc1a17165727f4c893.tar.xz
linux-320b2b8de12698082609ebbc1a17165727f4c893.zip
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 <keithp@keithp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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