Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20100908023549.BFFA8401AF@magilla.sf.frob.com>
Date: Tue,  7 Sep 2010 19:35:49 -0700 (PDT)
From: Roland McGrath <roland@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC: linux-kernel@...r.kernel.org, oss-security@...ts.openwall.com,
        Solar Designer <solar@...nwall.com>,
        Kees Cook <kees.cook@...onical.com>, Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
        Neil Horman <nhorman@...driver.com>, linux-fsdevel@...r.kernel.org,
        pageexec@...email.hu,
        "Brad Spengler <spender@...ecurity.net>
    Eugene Teo" <eugene@...hat.com>
Subject: [PATCH 1/3] 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@...hat.com>
---
 fs/exec.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 2d94552..1b63237 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -594,6 +594,11 @@ int setup_arg_pages(struct linux_binprm *bprm,
 #else
 	stack_top = arch_align_stack(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;
 
 	bprm->p -= stack_shift;

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.