1. 25 Jun, 2019 36 commits
  2. 22 Jun, 2019 4 commits
    • Greg Kroah-Hartman's avatar
      Linux 5.1.14 · 5f0a74b4
      Greg Kroah-Hartman authored
      5f0a74b4
    • Eric Dumazet's avatar
      tcp: refine memory limit test in tcp_fragment() · b27f2c88
      Eric Dumazet authored
      commit b6653b36 upstream.
      
      tcp_fragment() might be called for skbs in the write queue.
      
      Memory limits might have been exceeded because tcp_sendmsg() only
      checks limits at full skb (64KB) boundaries.
      
      Therefore, we need to make sure tcp_fragment() wont punish applications
      that might have setup very low SO_SNDBUF values.
      
      Fixes: f070ef2a ("tcp: tcp_fragment() should apply sane memory limits")
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Reported-by: default avatarChristoph Paasch <cpaasch@apple.com>
      Tested-by: default avatarChristoph Paasch <cpaasch@apple.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b27f2c88
    • Greg Kroah-Hartman's avatar
      Linux 5.1.13 · 7da3d9e6
      Greg Kroah-Hartman authored
      7da3d9e6
    • Andrea Arcangeli's avatar
      coredump: fix race condition between collapse_huge_page() and core dumping · d7dcfd25
      Andrea Arcangeli authored
      commit 59ea6d06 upstream.
      
      When fixing the race conditions between the coredump and the mmap_sem
      holders outside the context of the process, we focused on
      mmget_not_zero()/get_task_mm() callers in 04f5866e ("coredump: fix
      race condition between mmget_not_zero()/get_task_mm() and core
      dumping"), but those aren't the only cases where the mmap_sem can be
      taken outside of the context of the process as Michal Hocko noticed
      while backporting that commit to older -stable kernels.
      
      If mmgrab() is called in the context of the process, but then the
      mm_count reference is transferred outside the context of the process,
      that can also be a problem if the mmap_sem has to be taken for writing
      through that mm_count reference.
      
      khugepaged registration calls mmgrab() in the context of the process,
      but the mmap_sem for writing is taken later in the context of the
      khugepaged kernel thread.
      
      collapse_huge_page() after taking the mmap_sem for writing doesn't
      modify any vma, so it's not obvious that it could cause a problem to the
      coredump, but it happens to modify the pmd in a way that breaks an
      invariant that pmd_trans_huge_lock() relies upon.  collapse_huge_page()
      needs the mmap_sem for writing just to block concurrent page faults that
      call pmd_trans_huge_lock().
      
      Specifically the invariant that "!pmd_trans_huge()" cannot become a
      "pmd_trans_huge()" doesn't hold while collapse_huge_page() runs.
      
      The coredump will call __get_user_pages() without mmap_sem for reading,
      which eventually can invoke a lockless page fault which will need a
      functional pmd_trans_huge_lock().
      
      So collapse_huge_page() needs to use mmget_still_valid() to check it's
      not running concurrently with the coredump...  as long as the coredump
      can invoke page faults without holding the mmap_sem for reading.
      
      This has "Fixes: khugepaged" to facilitate backporting, but in my view
      it's more a bug in the coredump code that will eventually have to be
      rewritten to stop invoking page faults without the mmap_sem for reading.
      So the long term plan is still to drop all mmget_still_valid().
      
      Link: http://lkml.kernel.org/r/20190607161558.32104-1-aarcange@redhat.com
      Fixes: ba76149f ("thp: khugepaged")
      Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
      Reported-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Jann Horn <jannh@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
      Cc: Mike Kravetz <mike.kravetz@oracle.com>
      Cc: Peter Xu <peterx@redhat.com>
      Cc: Jason Gunthorpe <jgg@mellanox.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      d7dcfd25