From 6086741bda4d43cc227500bc7645a829380e6326 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Fri, 15 Feb 2019 09:21:45 +0100
Subject: [PATCH] CVE-2019-7572: Fix a buffer overwrite in IMA_ADPCM_decode
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If data chunk was longer than expected based on a WAV format
definition, IMA_ADPCM_decode() tried to write past the output
buffer. This patch fixes it.

Based on patch from
<https://bugzilla.libsdl.org/show_bug.cgi?id=4496>.

CVE-2019-7572
https://bugzilla.libsdl.org/show_bug.cgi?id=4495

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 src/audio/SDL_wave.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/audio/SDL_wave.c b/src/audio/SDL_wave.c
index 69d62dc..91e89e8 100644
--- a/src/audio/SDL_wave.c
+++ b/src/audio/SDL_wave.c
@@ -336,7 +336,7 @@ static void Fill_IMA_ADPCM_block(Uint8 *decoded, Uint8 *encoded,
 static int IMA_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
 {
 	struct IMA_ADPCM_decodestate *state;
-	Uint8 *freeable, *encoded, *encoded_end, *decoded;
+	Uint8 *freeable, *encoded, *encoded_end, *decoded, *decoded_end;
 	Sint32 encoded_len, samplesleft;
 	unsigned int c, channels;
 
@@ -363,6 +363,7 @@ static int IMA_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
 		return(-1);
 	}
 	decoded = *audio_buf;
+	decoded_end = decoded + *audio_len;
 
 	/* Get ready... Go! */
 	while ( encoded_len >= IMA_ADPCM_state.wavefmt.blockalign ) {
@@ -382,6 +383,7 @@ static int IMA_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
 			}
 
 			/* Store the initial sample we start with */
+			if (decoded + 2 > decoded_end) goto invalid_size;
 			decoded[0] = (Uint8)(state[c].sample&0xFF);
 			decoded[1] = (Uint8)(state[c].sample>>8);
 			decoded += 2;
@@ -392,6 +394,8 @@ static int IMA_ADPCM_decode(Uint8 **audio_buf, Uint32 *audio_len)
 		while ( samplesleft > 0 ) {
 			for ( c=0; c<channels; ++c ) {
 				if (encoded + 4 > encoded_end) goto invalid_size;
+				if (decoded + 4 * 4 * channels > decoded_end)
+					goto invalid_size;
 				Fill_IMA_ADPCM_block(decoded, encoded,
 						c, channels, &state[c]);
 				encoded += 4;
-- 
2.20.1

