Messages in this thread Patch in this message | | | From | Dan Smith <> | Subject | Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned | Date | Fri, 24 Feb 2012 11:19:25 -0800 |
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DR> but it doesn't "ensure" walk_page_range() always has start and end DR> addresses that are page aligned
Below is a changed version of the patch which always does the check. Since failing that condition indicates a kernel bug, WARN_ON() makes sure it gets some visibility.
Andrew, can you take this?
-- Dan Smith IBM Linux Technology Center email: danms@us.ibm.com
commit b06c2032d63f20d5a5513b3890776aeead397aa5 Author: Dan Smith <danms@us.ibm.com> Date: Fri Feb 24 11:07:05 2012 -0800
Ensure that walk_page_range()'s start and end are page-aligned
The inner function walk_pte_range() increments "addr" by PAGE_SIZE after each pte is processed, and only exits the loop if the result is equal to "end". Current, if either (or both of) the starting or ending addresses passed to walk_page_range() are not page-aligned, then we will never satisfy that exit condition and begin calling the pte_entry handler with bad data.
To be sure that we will land in the right spot, this patch checks that both "addr" and "end" are page-aligned in walk_page_range() before starting the traversal.
Signed-off-by: Dan Smith <danms@us.ibm.com> Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org
diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 2f5cf10..97ee963 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -196,6 +196,11 @@ int walk_page_range(unsigned long addr, unsigned long end, if (addr >= end) return err; + if (WARN_ONCE((addr & ~PAGE_MASK) || (end & ~PAGE_MASK), + "address range is not page-aligned")) { + return -EINVAL; + } + if (!walk->mm) return -EINVAL;
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