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From bb11ffcff5ae2f25bead921c2a299e7e63d8a759 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
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Date: Thu, 14 Feb 2019 16:51:54 +0100
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Subject: [PATCH] CVE-2019-7572: Fix a buffer overread in IMA_ADPCM_nibble
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If an IMA ADPCM block contained an initial index out of step table
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range (loaded in IMA_ADPCM_decode()), IMA_ADPCM_nibble() blindly used
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this bogus value and that lead to a buffer overread.
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This patch fixes it by moving clamping the index value at the
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beginning of IMA_ADPCM_nibble() function instead of the end after
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an update.
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CVE-2019-7572
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https://bugzilla.libsdl.org/show_bug.cgi?id=4495
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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src/audio/SDL_wave.c | 14 ++++++++------
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1 file changed, 8 insertions(+), 6 deletions(-)
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diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c
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index 2968b3d..69d62dc 100644
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--- a/src/audio/SDL_wave.c
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+++ b/src/audio/SDL_wave.c
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@@ -275,6 +275,14 @@ static Sint32 IMA_ADPCM_nibble(struct IMA_ADPCM_decodestate *state,Uint8 nybble)
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};
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Sint32 delta, step;
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+ /* Clamp index value. The inital value can be invalid. */
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+ if ( state->index > 88 ) {
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+ state->index = 88;
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+ } else
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+ if ( state->index < 0 ) {
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+ state->index = 0;
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+ }
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+
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/* Compute difference and new sample value */
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step = step_table[state->index];
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delta = step >> 3;
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@@ -286,12 +294,6 @@ static Sint32 IMA_ADPCM_nibble(struct IMA_ADPCM_decodestate *state,Uint8 nybble)
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/* Update index value */
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state->index += index_table[nybble];
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- if ( state->index > 88 ) {
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- state->index = 88;
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- } else
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- if ( state->index < 0 ) {
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- state->index = 0;
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- }
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/* Clamp output sample */
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if ( state->sample > max_audioval ) {
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--
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2.20.1
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