Eric Lee / linux-smarc-t335x-v3.2

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Commit 1b528181b2ffa14721fb28ad1bd539fe1732c583

Authored by Roland McGrath
Committed by Linus Torvalds
1 parent be6200aac9
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

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: Roland McGrath <roland@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 5 additions and 0 deletions Side-by-side Diff

... ... @@ -594,6 +594,11 @@
594 594 #else
595 595 stack_top = arch_align_stack(stack_top);
596 596 stack_top = PAGE_ALIGN(stack_top);
  597 +
  598 + if (unlikely(stack_top < mmap_min_addr) ||
  599 + unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
  600 + return -ENOMEM;
  601 +
597 602 stack_shift = vma->vm_end - stack_top;
598 603  
599 604 bprm->p -= stack_shift;