From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Wed, 13 Jan 2021 20:59:09 +1100
Subject: [PATCH] io/gzio: Bail if gzio->tl/td is NULL
This is an ugly fix that doesn't address why gzio->tl comes to be NULL.
However, it seems to be sufficient to patch up a bunch of NULL derefs.
It would be good to revisit this in future and see if we can have
a cleaner solution that addresses some of the causes of the unexpected
NULL pointers.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/io/gzio.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
index daf514bc482..09e0e2842f2 100644
--- a/grub-core/io/gzio.c
+++ b/grub-core/io/gzio.c
@@ -657,6 +657,13 @@ inflate_codes_in_window (grub_gzio_t gzio)
{
if (! gzio->code_state)
{
+
+ if (gzio->tl == NULL)
+ {
+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->tl");
+ return 1;
+ }
+
NEEDBITS ((unsigned) gzio->bl);
if ((e = (t = gzio->tl + ((unsigned) b & ml))->e) > 16)
do
@@ -695,6 +702,12 @@ inflate_codes_in_window (grub_gzio_t gzio)
n = t->v.n + ((unsigned) b & mask_bits[e]);
DUMPBITS (e);
+ if (gzio->td == NULL)
+ {
+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->td");
+ return 1;
+ }
+
/* decode distance of block to copy */
NEEDBITS ((unsigned) gzio->bd);
if ((e = (t = gzio->td + ((unsigned) b & md))->e) > 16)
@@ -905,6 +918,13 @@ init_dynamic_block (grub_gzio_t gzio)
n = nl + nd;
m = mask_bits[gzio->bl];
i = l = 0;
+
+ if (gzio->tl == NULL)
+ {
+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->tl");
+ return;
+ }
+
while ((unsigned) i < n)
{
NEEDBITS ((unsigned) gzio->bl);