3.6.11.9-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: yonghua zheng <younghua.zh...@gmail.com>

[ Upstream commit 8c8296223f3abb142be8fc31711b18a704c0e7d8 ]

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.

[a...@linux-foundation.org: document pagemapread.pos and .len units, fix 
PM_ENTRY_BYTES definition]
Signed-off-by: Yonghua Zheng <younghua.zh...@gmail.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Steven Rostedt <rost...@goodmis.org>
---
 fs/proc/task_mmu.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4540b8f..1868fe1 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -693,14 +693,14 @@ typedef struct {
 } pagemap_entry_t;
 
 struct pagemapread {
-       int pos, len;
+       int pos, len;           /* units: PM_ENTRY_BYTES, not bytes */
        pagemap_entry_t *buffer;
 };
 
 #define PAGEMAP_WALK_SIZE      (PMD_SIZE)
 #define PAGEMAP_WALK_MASK      (PMD_MASK)
 
-#define PM_ENTRY_BYTES      sizeof(u64)
+#define PM_ENTRY_BYTES      sizeof(pagemap_entry_t)
 #define PM_STATUS_BITS      3
 #define PM_STATUS_OFFSET    (64 - PM_STATUS_BITS)
 #define PM_STATUS_MASK      (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET)
@@ -939,8 +939,8 @@ static ssize_t pagemap_read(struct file *file, char __user 
*buf,
        if (!count)
                goto out_task;
 
-       pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
-       pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
+       pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
+       pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
        ret = -ENOMEM;
        if (!pm.buffer)
                goto out_task;
-- 
1.7.10.4


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Reply via email to