Messages in this thread Patch in this message | | | Subject | Re: [patch 0/3] no MAX_ARG_PAGES -v2 | From | Peter Zijlstra <> | Date | Fri, 15 Jun 2007 11:24:38 +0200 |
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On Thu, 2007-06-14 at 13:58 -0700, Ollie Wild wrote:
> A good heuristic, though, might be to limit > argument size to a percentage (say 25%) of maximum stack size and > validate this inside copy_strings().
This seems to do:
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- fs/exec.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
Index: linux-2.6-2/fs/exec.c =================================================================== --- linux-2.6-2.orig/fs/exec.c 2007-06-15 11:05:09.000000000 +0200 +++ linux-2.6-2/fs/exec.c 2007-06-15 11:05:18.000000000 +0200 @@ -199,6 +199,23 @@ static struct page *get_arg_page(struct if (ret <= 0) return NULL; + if (write) { + struct rlimit *rlim = current->signal->rlim; + unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; + + /* + * Limit to 1/4-th the stack size for the argv+env strings. + * This ensures that: + * - the remaining binfmt code will not run out of stack space, + * - the program will have a reasonable amount of stack left + * to work from. + */ + if (size > rlim[RLIMIT_STACK].rlim_cur / 4) { + put_page(page); + return NULL; + } + } + return page; }
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