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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Wed, 13 Jan 2021 20:59:09 +1100
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Subject: [PATCH] io/gzio: Bail if gzio->tl/td is NULL
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This is an ugly fix that doesn't address why gzio->tl comes to be NULL.
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However, it seems to be sufficient to patch up a bunch of NULL derefs.
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It would be good to revisit this in future and see if we can have
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a cleaner solution that addresses some of the causes of the unexpected
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NULL pointers.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/io/gzio.c | 20 ++++++++++++++++++++
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1 file changed, 20 insertions(+)
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diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
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index 2ecf076dd..6e9b9c936 100644
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--- a/grub-core/io/gzio.c
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+++ b/grub-core/io/gzio.c
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@@ -669,6 +669,13 @@ inflate_codes_in_window (grub_gzio_t gzio)
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{
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if (! gzio->code_state)
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{
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+
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+ if (gzio->tl == NULL)
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+ {
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+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->tl");
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+ return 1;
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+ }
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+
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NEEDBITS ((unsigned) gzio->bl);
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if ((e = (t = gzio->tl + ((unsigned) b & ml))->e) > 16)
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do
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@@ -707,6 +714,12 @@ inflate_codes_in_window (grub_gzio_t gzio)
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n = t->v.n + ((unsigned) b & mask_bits[e]);
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DUMPBITS (e);
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+ if (gzio->td == NULL)
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+ {
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+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->td");
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+ return 1;
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+ }
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+
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/* decode distance of block to copy */
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NEEDBITS ((unsigned) gzio->bd);
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if ((e = (t = gzio->td + ((unsigned) b & md))->e) > 16)
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@@ -917,6 +930,13 @@ init_dynamic_block (grub_gzio_t gzio)
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n = nl + nd;
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m = mask_bits[gzio->bl];
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i = l = 0;
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+
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+ if (gzio->tl == NULL)
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+ {
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+ grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "NULL gzio->tl");
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+ return;
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+ }
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+
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while ((unsigned) i < n)
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{
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NEEDBITS ((unsigned) gzio->bl);
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