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authorOleg Nesterov <oleg@redhat.com>2012-07-29 20:22:16 +0200
committerIngo Molnar <mingo@kernel.org>2012-07-30 11:27:19 +0200
commitc517ee744b96e441d9c731e245f83c6d08dc0a19 (patch)
tree8d7f7b86767ba2d5c62c2d421f388949f0483c85 /kernel
parentf403072c6108e15f319a4a5036b650c77760522c (diff)
uprobes: __replace_page() should not use page_address_in_vma()
page_address_in_vma(old_page) in __replace_page() is ugly and wrong. The caller already knows the correct virtual address, this page was found by get_user_pages(vaddr). However, page_address_in_vma() can actually fail if page->mapping was cleared by __delete_from_page_cache() after get_user_pages() returns. But this means the race with page reclaim, write_opcode() should not fail, it should retry and read this page again. Probably the race with remove_mapping() is not possible due to page_freeze_refs() logic, but afaics at least shmem_writepage()->shmem_delete_from_page_cache() can clear ->mapping. We could change __replace_page() to return -EAGAIN in this case, but it would be better to simply use the caller's vaddr and rely on page_check_address(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com> Cc: Anton Arapov <anton@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20120729182216.GA20311@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/uprobes.c11
1 files changed, 4 insertions, 7 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a2b32a51d0a..6fda7996892 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -127,22 +127,19 @@ static loff_t vma_address(struct vm_area_struct *vma, loff_t offset)
* based on replace_page in mm/ksm.c
*
* @vma: vma that holds the pte pointing to page
+ * @addr: address the old @page is mapped at
* @page: the cowed page we are replacing by kpage
* @kpage: the modified page we replace page by
*
* Returns 0 on success, -EFAULT on failure.
*/
-static int __replace_page(struct vm_area_struct *vma, struct page *page, struct page *kpage)
+static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
+ struct page *page, struct page *kpage)
{
struct mm_struct *mm = vma->vm_mm;
- unsigned long addr;
spinlock_t *ptl;
pte_t *ptep;
- addr = page_address_in_vma(page, vma);
- if (addr == -EFAULT)
- return -EFAULT;
-
ptep = page_check_address(page, mm, addr, &ptl, 0);
if (!ptep)
return -EAGAIN;
@@ -243,7 +240,7 @@ retry:
goto unlock_out;
lock_page(new_page);
- ret = __replace_page(vma, old_page, new_page);
+ ret = __replace_page(vma, vaddr, old_page, new_page);
unlock_page(new_page);
unlock_out: