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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: Thu, 21 Jan 2021 00:05:58 +1100
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Subject: [PATCH] io/gzio: Add init_dynamic_block() clean up if unpacking codes
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fails
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init_dynamic_block() didn't clean up gzio->tl and td in some error
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paths. This left td pointing to part of tl. Then in grub_gzio_close(),
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when tl was freed the storage for td would also be freed. The code then
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attempts to free td explicitly, performing a UAF and then a double free.
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Explicitly clean up tl and td in the error paths.
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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 | 12 +++++++++---
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1 file changed, 9 insertions(+), 3 deletions(-)
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diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
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index 6e9b9c9361a..97b34f88574 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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@@ -953,7 +953,7 @@ init_dynamic_block (grub_gzio_t gzio)
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if ((unsigned) i + j > n)
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{
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grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
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- return;
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+ goto fail;
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}
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while (j--)
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ll[i++] = l;
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@@ -966,7 +966,7 @@ init_dynamic_block (grub_gzio_t gzio)
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if ((unsigned) i + j > n)
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{
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grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
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- return;
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+ goto fail;
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}
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while (j--)
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ll[i++] = 0;
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@@ -981,7 +981,7 @@ init_dynamic_block (grub_gzio_t gzio)
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if ((unsigned) i + j > n)
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{
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grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
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- return;
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+ goto fail;
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}
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while (j--)
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ll[i++] = 0;
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@@ -1019,6 +1019,12 @@ init_dynamic_block (grub_gzio_t gzio)
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/* indicate we're now working on a block */
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gzio->code_state = 0;
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gzio->block_len++;
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+ return;
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+
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+ fail:
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+ huft_free (gzio->tl);
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+ gzio->td = NULL;
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+ gzio->tl = NULL;
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}
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