apedec: prevent out of array writes in decode_array_0000

s->decoded_buffer is allocated with a min_size of:
    2 * FFALIGN(blockstodecode, 8) * sizeof(*s->decoded_buffer)

Then it is assigned to s->decoded[0] (and s->decoded_buffer + FFALIGN(blockstodecode, 8)
to s->decoded[1]) and passed as out buffer to decode_array_0000.

In this function 64 elements of the out buffer are written
unconditionally and outside the array if blockstodecode is too small.

This causes memory corruption, leading to segmentation faults or other
crashes.

Thus change decode_array_0000 to write at most blockstodecode elements
of the out buffer.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 699341d647f7af785fb8ceed67604467b0b9ab12)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
This commit is contained in:
Andreas Cadhalpun 2015-04-28 11:13:43 +02:00
parent d35086d715
commit 9f2c8734b9

View File

@ -592,14 +592,14 @@ static void decode_array_0000(APEContext *ctx, GetBitContext *gb,
int ksummax, ksummin;
rice->ksum = 0;
for (i = 0; i < 5; i++) {
for (i = 0; i < FFMIN(blockstodecode, 5); i++) {
out[i] = get_rice_ook(&ctx->gb, 10);
rice->ksum += out[i];
}
rice->k = av_log2(rice->ksum / 10) + 1;
if (rice->k >= 24)
return;
for (; i < 64; i++) {
for (; i < FFMIN(blockstodecode, 64); i++) {
out[i] = get_rice_ook(&ctx->gb, rice->k);
rice->ksum += out[i];
rice->k = av_log2(rice->ksum / ((i + 1) * 2)) + 1;