[PATCH 1/2] pstore: fix NULL pointer fault if get NULL prz in ramoops_get_next_prz

[Liu ShuoX <shuox.liu@intel.com>]

These two patches are applied on top of patches:
https://lkml.org/lkml/2014/3/3/368
It has been added in -mm tree. Below is the first patch, and i will
send the second by replying this one.

From: Liu ShuoX <shuox.liu@intel.com>

ramoops_get_next_prz get the prz according the paramters. If it get a
uninitialized prz, access its members by following persistent_ram_old_size(prz)
will cause a NULL pointer crash.
Ex: if ftrace_size is 0, fprz will be NULL.

Fix it by return NULL in advance.

Signed-off-by: Liu ShuoX <shuox.liu@intel.com>
---
  fs/pstore/ram.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1daed28..6f96d8c 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -119,6 +119,8 @@ ramoops_get_next_prz(struct persistent_ram_zone *przs[], uint *c, uint max,
  		return NULL;
  
  	prz = przs[i];
+	if (!prz)
+		return NULL;
  
  	/* Update old/shadowed buffer. */
  	if (update)
-- 
1.8.3.2