[tip:perf/core] uprobes: __copy_insn() should ensure a_ops->readpage != NULL

[tip-bot for Oleg Nesterov]

Commit-ID:  cc359d180fa9c25a4c1819f17e07a422d788353d
Gitweb:     http://git.kernel.org/tip/cc359d180fa9c25a4c1819f17e07a422d788353d
Author:     Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Fri, 15 Jun 2012 17:43:25 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 16 Jun 2012 09:10:42 +0200

uprobes: __copy_insn() should ensure a_ops->readpage != NULL

__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@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Anton Arapov <anton@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20120615154325.GA9568@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/events/uprobes.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index f0d0453..604930b 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -610,6 +610,9 @@ __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;
 
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