From: yonghua zheng <younghua.zheng@gmail.com>
Date: Tue, 13 Aug 2013 23:01:03 +0000 (-0700)
Subject: fs/proc/task_mmu.c: fix buffer overflow in add_page_map()
X-Git-Tag: v3.2.51~50
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bd20948dc24c3a1cf5ea18385943783f11c2c751;p=pandora-kernel.git

fs/proc/task_mmu.c: fix buffer overflow in add_page_map()

commit 8c8296223f3abb142be8fc31711b18a704c0e7d8 upstream.

Recently we met quite a lot of random kernel panic issues after enabling
CONFIG_PROC_PAGE_MONITOR.  After debuggind we found this has something
to do with following bug in pagemap:

In struct pagemapread:

  struct pagemapread {
      int pos, len;
      pagemap_entry_t *buffer;
      bool v2;
  };

pos is number of PM_ENTRY_BYTES in buffer, but len is the size of
buffer, it is a mistake to compare pos and len in add_page_map() for
checking buffer is full or not, and this can lead to buffer overflow and
random kernel panic issue.

Correct len to be total number of PM_ENTRY_BYTES in buffer.

[akpm@linux-foundation.org: document pagemapread.pos and .len units, fix PM_ENTRY_BYTES definition]
Signed-off-by: Yonghua Zheng <younghua.zheng@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2:
 - Adjust context
 - There is no pagemap_entry_t definition; keep using u64]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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