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Subjectsound/pci/ac97/ac97_patch.c: possible negative array index
The Coverity checker noted the following in sound/pci/ac97/ac97_patch.c:

<-- snip -->

...
static int patch_ad1881_chained1(struct snd_ac97 * ac97, int idx, unsigned short codec_bits)
{
static int cfg_bits[3] = { 1<<12, 1<<14, 1<<13 };
unsigned short val;
snd_ac97_update_bits(ac97, AC97_AD_SERIAL_CFG, 0x7000, cfg_bits[idx]);
snd_ac97_write_cache(ac97, AC97_AD_CODEC_CFG, 0x0004); // SDIE
val = snd_ac97_read(ac97, AC97_VENDOR_ID2);
if ((val & 0xff40) != 0x5340)
return 0;
if (codec_bits)
snd_ac97_write_cache(ac97, AC97_AD_CODEC_CFG, codec_bits);
ac97->spec.ad18xx.chained[idx] = cfg_bits[idx];
ac97->spec.ad18xx.id[idx] = val;
ac97->spec.ad18xx.codec_cfg[idx] = codec_bits ? codec_bits : 0x0004;
return 1;
}
static void patch_ad1881_chained(struct snd_ac97 * ac97, int unchained_idx, int cidx1, int cidx2)
{
// already detected?
if (ac97->spec.ad18xx.unchained[cidx1] || ac97->spec.ad18xx.chained[cidx1])
cidx1 = -1;
if (ac97->spec.ad18xx.unchained[cidx2] || ac97->spec.ad18xx.chained[cidx2])
cidx2 = -1;
if (cidx1 < 0 && cidx2 < 0)
return;
// test for chained codecs
snd_ac97_update_bits(ac97, AC97_AD_SERIAL_CFG, 0x7000,
ac97->spec.ad18xx.unchained[unchained_idx]);
snd_ac97_write_cache(ac97, AC97_AD_CODEC_CFG, 0x0002); // ID1C
ac97->spec.ad18xx.codec_cfg[unchained_idx] = 0x0002;
if (cidx1 >= 0) {
if (patch_ad1881_chained1(ac97, cidx1, 0x0006)) // SDIE | ID1C
patch_ad1881_chained1(ac97, cidx2, 0);
else if (patch_ad1881_chained1(ac97, cidx2, 0x0006)) // SDIE | ID1C
patch_ad1881_chained1(ac97, cidx1, 0);
} else if (cidx2 >= 0) {
patch_ad1881_chained1(ac97, cidx2, 0);
}
}
...
<-- snip -->

If there are in patch_ad1881_chained() (cidx2 == -1) and (cidx1 >= 0),
-1 will be used as array index in patch_ad1881_chained1().

cu
Adrian

--

"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

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