linux-kernel - [PATCH] Restrict stack space reservation to rlimit

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Date:	Mon, 08 Feb 2010 11:07:52 +1100
From:	Michael Neuling <mikey@...ling.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	James Morris <jmorris@...ei.org>, Ingo Molnar <mingo@...e.hu>,
	linux-fsdevel@...r.kernel.org, Anton Blanchard <anton@...ba.org>,
	stable@...nel.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, Serge Hallyn <serue@...ibm.com>,
	WANG Cong <xiyou.wangcong@...il.com>,
	Paul Mackerras <paulus@...ba.org>, benh@...nel.crashing.org,
	miltonm@....com, aeb@....nl
Subject: [PATCH] Restrict stack space reservation to rlimit

apkm, linus: this or something like it needs to go into 2.6.33 (& 32) to
fix 'ulimit -s'.  

Mikey

[PATCH] Restrict stack space reservation to rlimit

When reserving stack space for a new process, make sure we're not
attempting to allocate more than rlimit allows.

Also, reserve the same stack size independent of page size.

This fixes a bug unmasked by fc63cf237078c86214abcb2ee9926d8ad289da9b

Signed-off-by: Michael Neuling <mikey@...ling.org>
Cc: Anton Blanchard <anton@...ba.org>
Cc: stable@...nel.org
---
 fs/exec.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: clone1/fs/exec.c
===================================================================
--- clone1.orig/fs/exec.c
+++ clone1/fs/exec.c
@@ -554,7 +554,7 @@ static int shift_arg_pages(struct vm_are
 	return 0;
 }
 
-#define EXTRA_STACK_VM_PAGES	20	/* random */
+#define EXTRA_STACK_VM_SIZE	81920UL	/* randomly 20 4K pages */
 
 /*
  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
@@ -627,10 +627,13 @@ int setup_arg_pages(struct linux_binprm 
 			goto out_unlock;
 	}
 
+	stack_base = min(EXTRA_STACK_VM_SIZE,
+			 current->signal->rlim[RLIMIT_STACK].rlim_cur) -
+		PAGE_SIZE;
 #ifdef CONFIG_STACK_GROWSUP
-	stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
+	stack_base = vma->vm_end + stack_base;
 #else
-	stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
+	stack_base = vma->vm_start - stack_base;
 #endif
 	ret = expand_stack(vma, stack_base);
 	if (ret)
--
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