Re: [PATCH] Use correct page protection for put_dirty_page

William Lee Irwin III (wli@holomorphy.com)
Sun, 11 May 2003 01:30:35 -0700


On Sun, May 11, 2003 at 10:08:41AM +0200, Andi Kleen wrote:
> put_page_dirty must use the page protection of the stack VMA, not hardcoded
> PAGE_COPY. They can be different e.g. when the stack is set non executable
> via VM_STACK_FLAGS.
> I added an fallback path for now because I'm not sure if the stack VMA
> is always predowngrowed here, if the printk better it may be also needed
> to add an stack extension here.

We know which vma is involved at the callsite and what we just set its
vma->vm_page_prot to; I suggest this patch instead.

-- wli

diff -prauN linux-2.5.69-1/fs/exec.c exec-2.5.69-1/fs/exec.c
--- linux-2.5.69-1/fs/exec.c Wed Apr 16 15:34:51 2003
+++ exec-2.5.69-1/exec.c Sun May 11 01:27:47 2003
@@ -314,7 +314,7 @@
}
lru_cache_add_active(page);
flush_dcache_page(page);
- set_pte(pte, pte_mkdirty(pte_mkwrite(mk_pte(page, PAGE_COPY))));
+ set_pte(pte, pte_mkdirty(pte_mkwrite(mk_pte(page, protection_map[VM_STACK_FLAGS & 0x7]))));
pte_chain = page_add_rmap(page, pte, pte_chain);
pte_unmap(pte);
tsk->mm->rss++;
-
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