1. 02 Jul, 2017 1 commit
    • Linus Torvalds's avatar
      mm: do not grow the stack vma just because of an overrun on preceding vma · 641fbf59
      Linus Torvalds authored
      commit 09884964 upstream.
      
      The stack vma is designed to grow automatically (marked with VM_GROWSUP
      or VM_GROWSDOWN depending on architecture) when an access is made beyond
      the existing boundary.  However, particularly if you have not limited
      your stack at all ("ulimit -s unlimited"), this can cause the stack to
      grow even if the access was really just one past *another* segment.
      
      And that's wrong, especially since we first grow the segment, but then
      immediately later enforce the stack guard page on the last page of the
      segment.  So _despite_ first growing the stack segment as a result of
      the access, the kernel will then make the access cause a SIGSEGV anyway!
      
      So do the same logic as the guard page check does, and consider an
      access to within one page of the next segment to be a bad access, rather
      than growing the stack to abut the next segment.
      Reported-and-tested-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
      641fbf59
  2. 05 Jun, 2017 39 commits