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Subject[PATCH] [16/16] POISON: Add madvise() based injector for poisoned data
Date

Impact: optional, useful for debugging

Add a new madvice sub command to inject poison for some
pages in a process' address space. This is useful for
testing the poison page handling.

Open issues:

- This patch allows root to tie up arbitary amounts of memory.
Should this be disabled inside containers?
- There's a small race window between getting the page and injecting.
The patch drops the ref count because otherwise memory_failure
complains about dangling references. In theory with a multi threaded
injector one could inject poison for a process foreign page this way.
Not a serious issue right now.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
include/asm-generic/mman.h | 1 +
mm/madvise.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)
Index: linux/mm/madvise.c
===================================================================
--- linux.orig/mm/madvise.c 2009-04-07 16:36:29.000000000 +0200
+++ linux/mm/madvise.c 2009-04-07 16:39:39.000000000 +0200
@@ -208,6 +208,38 @@
return error;
}

+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Error injection support for memory error handling.
+ */
+static int madvise_poison(unsigned long start, unsigned long end)
+{
+ /*
+ * RED-PEN
+ * This allows to tie up arbitary amounts of memory.
+ * Might be a good idea to disable it inside containers even for root.
+ */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ for (; start < end; start += PAGE_SIZE) {
+ struct page *p;
+ int ret = get_user_pages(current, current->mm, start, 1,
+ 0, 0, &p, NULL);
+ if (ret != 1)
+ return ret;
+ put_page(p);
+ /*
+ * RED-PEN page can be reused, but otherwise we'll have to fight with the
+ * refcnt
+ */
+ printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
+ page_to_pfn(p), start);
+ memory_failure(page_to_pfn(p), 0);
+ }
+ return 0;
+}
+#endif
+
static long
madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
unsigned long start, unsigned long end, int behavior)
@@ -290,6 +322,11 @@
int write;
size_t len;

+#ifdef CONFIG_MEMORY_FAILURE
+ if (behavior == MADV_POISON)
+ return madvise_poison(start, start+len_in);
+#endif
+
write = madvise_need_mmap_write(behavior);
if (write)
down_write(&current->mm->mmap_sem);
Index: linux/include/asm-generic/mman.h
===================================================================
--- linux.orig/include/asm-generic/mman.h 2009-04-07 16:36:29.000000000 +0200
+++ linux/include/asm-generic/mman.h 2009-04-07 16:39:39.000000000 +0200
@@ -34,6 +34,7 @@
#define MADV_REMOVE 9 /* remove these pages & resources */
#define MADV_DONTFORK 10 /* don't inherit across fork */
#define MADV_DOFORK 11 /* do inherit across fork */
+#define MADV_POISON 12 /* poison the page (root only) */

/* compatibility flags */
#define MAP_FILE 0

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