From 06d20617d0d5bb89a6caf5f2201c93baf03c43c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Mon, 10 Jun 2019 08:54:29 -0700
Subject: [PATCH 05/11] CVE-2019-7577: Fix a buffer overread in MS_ADPCM_nibble
 and MS_ADPCM_decode If a chunk of RIFF/WAV file with MS ADPCM encoding
 contains an invalid predictor (a valid predictor's value is between 0 and 6
 inclusive), a buffer overread can happen when the predictor is used as an
 index into an array of MS ADPCM coefficients.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The overead happens when indexing MS_ADPCM_state.aCoeff[] array in
MS_ADPCM_decode() and later when dereferencing a coef pointer in
MS_ADPCM_nibble().

This patch fixes it by checking the MS ADPCM predictor values fit
into the valid range.

CVE-2019-7577
Reproducer: https://bugzilla.libsdl.org/show_bug.cgi?id=4492

Signed-off-by: Petr Písař <ppisar@redhat.com>

--HG--
branch : SDL-1.2
---
 src/audio/SDL_wave.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c
index 6c6eb14eb..3eedd20a1 100644
--- a/src/audio/SDL_wave.c
+++ b/src/audio/SDL_wave.c
@@ -147,6 +147,9 @@ static int MS_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
 		if ( stereo ) {
 			state[1]->hPredictor = *encoded++;
 		}
+		if (state[0]->hPredictor >= 7 || state[1]->hPredictor >= 7) {
+			goto invalid_predictor;
+		}
 		state[0]->iDelta = ((encoded[1]<<8)|encoded[0]);
 		encoded += sizeof(Sint16);
 		if ( stereo ) {
@@ -217,6 +220,10 @@ too_short:
 	SDL_SetError("Too short chunk for a MS ADPCM decoder");
 	SDL_free(freeable);
 	return(-1);
+invalid_predictor:
+	SDL_SetError("Invalid predictor value for a MS ADPCM decoder");
+	SDL_free(freeable);
+	return(-1);
 }
 
 struct IMA_ADPCM_decodestate {
-- 
2.21.0