From mboxrd@z Thu Jan 1 00:00:00 1970 From: Helge Deller Subject: Re: [PATCH] Restrict initial stack space expansion to rlimit Date: Tue, 09 Feb 2010 23:27:08 +0100 Message-ID: <4B71E13C.2050905@gmx.de> References: <20100208161014.7C6D.A69D9226@jp.fujitsu.com> <1273.1265695885@neuling.org> <20100209154141.03F0.A69D9226@jp.fujitsu.com> <11046.1265705967@neuling.org> <20100209132529.bfc455b7.akpm@linux-foundation.org> <10733.1265752289@neuling.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Andrew Morton , KOSAKI Motohiro , Americo Wang , Anton Blanchard , Linus Torvalds , Alexander Viro , Oleg Nesterov , James Morris , Ingo Molnar , linux-fsdevel@vger.kernel.org, stable@kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Serge Hallyn , Paul Mackerras , benh@kernel.crashing.org, miltonm@bga.com, aeb@cwi.nl, linux-parisc@vger.kernel.org To: Michael Neuling Return-path: In-Reply-To: <10733.1265752289@neuling.org> List-ID: List-Id: linux-parisc.vger.kernel.org On 02/09/2010 10:51 PM, Michael Neuling wrote: >>> I'd still like someone with a CONFIG_STACK_GROWSUP arch to test/ACK it >>> as well. >> >> There's only one CONFIG_GROWSUP arch - parisc. >> Could someone please test it on parisc? I did. > How about doing: > '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. > > I'm suggesting 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 on parisc should be fine to test with. Mikey, thanks for the suggested test plan. I'm not sure if your patch does it correct for parisc/stack-grows-up-case. I tested your patch on a 4k pages kernel: root@c3000:~# uname -a Linux c3000 2.6.33-rc7-32bit #221 Tue Feb 9 23:17:06 CET 2010 parisc GNU/Linux Without your patch: root@c3000:~# ulimit -s 15; ls Killed -> correct. With your patch: root@c3000:~# ulimit -s 15; ls Killed _or_: root@c3000:~# ulimit -s 15; ls Segmentation fault -> ?? Any idea? Helge >> From: Michael Neuling >> >> 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 b6a2fea39318e43fee84fa7b0b90d68bed92d2ba ("mm: >> variable length argument support") and unmasked by >> fc63cf237078c86214abcb2ee9926d8ad289da9b ("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. >> >> Signed-off-by: Michael Neuling >> Cc: KOSAKI Motohiro >> Cc: Americo Wang >> Cc: Anton Blanchard >> Cc: Oleg Nesterov >> Cc: James Morris >> Cc: Ingo Molnar >> Cc: Serge Hallyn >> Cc: Benjamin Herrenschmidt >> Cc: >> >> fs/exec.c | 21 +++++++++++++++++++-- >> 1 file changed, 19 insertions(+), 2 deletions(-) >> >> diff -puN fs/exec.c~fs-execc-restrict-initial-stack-space-expansion-to-rlimit > fs/exec.c >> --- a/fs/exec.c~fs-execc-restrict-initial-stack-space-expansion-to-rlimit >> +++ a/fs/exec.c >> @@ -571,6 +571,9 @@ int setup_arg_pages(struct linux_binprm >> struct vm_area_struct *prev = NULL; >> unsigned long vm_flags; >> unsigned long stack_base; >> + unsigned long stack_size; >> + unsigned long stack_expand; >> + unsigned long rlim_stack; >> >> #ifdef CONFIG_STACK_GROWSUP >> /* Limit stack size to 1GB */ >> @@ -627,10 +630,24 @@ int setup_arg_pages(struct linux_binprm >> goto out_unlock; >> } >> >> + stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; >> + stack_size = vma->vm_end - vma->vm_start; >> + /* >> + * Align this down to a page boundary as expand_stack >> + * will align it up. >> + */ >> + rlim_stack = rlimit(RLIMIT_STACK)& PAGE_MASK; >> + rlim_stack = min(rlim_stack, stack_size); >> #ifdef CONFIG_STACK_GROWSUP >> - stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE; >> + if (stack_size + stack_expand> rlim_stack) >> + stack_base = vma->vm_start + rlim_stack; >> + else >> + stack_base = vma->vm_end + stack_expand; >> #else >> - stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE; >> + if (stack_size + stack_expand> rlim_stack) >> + stack_base = vma->vm_end - rlim_stack; >> + else >> + stack_base = vma->vm_start - stack_expand; >> #endif >> ret = expand_stack(vma, stack_base); >> if (ret)