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| author | Oleg Nesterov <oleg@redhat.com> | 2012-07-29 20:22:16 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2012-07-30 11:27:19 +0200 |
| commit | c517ee744b96e441d9c731e245f83c6d08dc0a19 (patch) | |
| tree | 8d7f7b86767ba2d5c62c2d421f388949f0483c85 /kernel/events | |
| parent | uprobes: Don't recheck vma/f_mapping in write_opcode() (diff) | |
| download | linux-c517ee744b96e441d9c731e245f83c6d08dc0a19.tar.xz linux-c517ee744b96e441d9c731e245f83c6d08dc0a19.zip | |
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/events')
| -rw-r--r-- | kernel/events/uprobes.c | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index a2b32a51d0a2..6fda7996892b 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: |