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