pstore: Fix NULL pointer fault if get NULL prz in ramoops_get_next_prz

commit b0aa931fb84431394d995472d0af2a6c2b61064d upstream.

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>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: HuKeping <hukeping@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index e0e42b5a691ced15ce979fbd6944028c2010f3a3..d3d37142bd93b49c9e3d6c0b11063d8af17d15f3 100644 (file)
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -125,6 +125,8 @@ 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)