[PATCH 2/3] uprobes: __copy_insn() should ensure a_ops->readpage != NULL

[Oleg Nesterov <oleg@redhat.com>]

__copy_insn() blindly calls read_mapping_page(), this will crash
the kernel if ->readpage == NULL, add the necessary check. For
example, hugetlbfs_aops->readpage is NULL. Perhaps we should change
read_mapping_page() instead.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/events/uprobes.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 48d53af..9c53bc2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -616,6 +616,8 @@ __copy_insn(struct address_space *mapping, struct vm_area_struct *vma, char *ins
 
 	if (!filp)
 		return -EINVAL;
+	if (!mapping->a_ops->readpage)
+		return -EIO;
 
 	idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
 	off1 = offset &= ~PAGE_MASK;
-- 
1.5.5.1