Commit 1b528181 authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds

setup_arg_pages: diagnose excessive argument size

The CONFIG_STACK_GROWSDOWN variant of setup_arg_pages() does not
check the size of the argument/environment area on the stack.
When it is unworkably large, shift_arg_pages() hits its BUG_ON.
This is exploitable with a very large RLIMIT_STACK limit, to
create a crash pretty easily.

Check that the initial stack is not too large to make it possible
to map in any executable.  We're not checking that the actual
executable (or intepreter, for binfmt_elf) will fit.  So those
mappings might clobber part of the initial stack mapping.  But
that is just userland lossage that userland made happen, not a
kernel problem.
Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent be6200aa
...@@ -594,6 +594,11 @@ int setup_arg_pages(struct linux_binprm *bprm, ...@@ -594,6 +594,11 @@ int setup_arg_pages(struct linux_binprm *bprm,
#else #else
stack_top = arch_align_stack(stack_top); stack_top = arch_align_stack(stack_top);
stack_top = PAGE_ALIGN(stack_top); stack_top = PAGE_ALIGN(stack_top);
if (unlikely(stack_top < mmap_min_addr) ||
unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
return -ENOMEM;
stack_shift = vma->vm_end - stack_top; stack_shift = vma->vm_end - stack_top;
bprm->p -= stack_shift; bprm->p -= stack_shift;
......
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