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From: =?utf-8?b?UGV0ciBQw61zYcWZ?= <ppisar@redhat.com>
Date: Sat, 8 Jun 2019 17:57:43 -0700
Subject: 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.
Bug: https://bugzilla.libsdl.org/show_bug.cgi?id=4495
Bug-CVE: CVE-2019-7572
Signed-off-by: Petr Písař <ppisar@redhat.com>
Origin: upstream, commit:https://github.com/libsdl-org/SDL-1.2/commit/1ead4913fc2314a0ce5de06f29a20a8b0b0a5557
---
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 b4ad6c7..ba1fb52 100644
--- a/src/audio/SDL_wave.c
+++ b/src/audio/SDL_wave.c
@@ -264,6 +264,14 @@ 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;
@@ -275,12 +283,6 @@ 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 ) {
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