• Michael Neuling's avatar
    fs/exec.c: restrict initial stack space expansion to rlimit · 803bf5ec
    Michael Neuling authored
    When reserving stack space for a new process, make sure we're not
    attempting to expand the stack by more than rlimit allows.
    This fixes a bug caused by b6a2fea3 ("mm:
    variable length argument support") and unmasked by
    fc63cf23 ("exec: setup_arg_pages() fails
    to return errors").
    This bug means that when limiting the stack to less the 20*PAGE_SIZE (eg.
    80K on 4K pages or 'ulimit -s 79') all processes will be killed before
    they start.  This is particularly bad with 64K pages, where a ulimit below
    1280K will kill every process.
    To test, do:
      'ulimit -s 15; ls'
    before and after the patch is applied.  Before it's applied, 'ls' should
    be killed.  After the patch is applied, 'ls' should no longer be killed.
    A stack limit of 15KB since it's small enough to trigger 20*PAGE_SIZE.
    Also 15KB not a multiple of PAGE_SIZE, which is a trickier case to handle
    correctly with this code.
    4K pages should be fine to test with.
    [kosaki.motohiro@jp.fujitsu.com: cleanup]
    [akpm@linux-foundation.org: cleanup cleanup]
    Signed-off-by: default avatarMichael Neuling <mikey@neuling.org>
    Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Americo Wang <xiyou.wangcong@gmail.com>
    Cc: Anton Blanchard <anton@samba.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: James Morris <jmorris@namei.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Serge Hallyn <serue@us.ibm.com>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: <stable@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
exec.c 45.2 KB