uprobes: No need to re-check vma_address() in write_opcode()

write_opcode() is called by register_for_each_vma() and
uprobe_mmap() paths. In both cases the caller has already
verified this vaddr under mmap_sem, no need to re-check.

Note also that this check is wrong anyway, we should not
truncate loff_t returned by vma_address() if we do not trust
this mapping.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154347.GA9604@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2db1d94..14c71a2 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -211,7 +211,6 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
        struct vm_area_struct *vma;
        struct uprobe *uprobe;
        unsigned long pgoff;
-       loff_t addr;
        int ret;
 retry:
        /* Read the page with vaddr into memory */
@@ -235,10 +234,6 @@ retry:
        if (mapping != vma->vm_file->f_mapping)
                goto put_out;
 
-       addr = vma_address(vma, uprobe->offset);
-       if (vaddr != (unsigned long)addr)
-               goto put_out;
-
        ret = -ENOMEM;
        new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
        if (!new_page)