3.16.63-rc1 review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
commit 7194eda1ba0872d917faf3b322540b4f57f11ba5 upstream.
The function snd_ac97_put_spsa() gets the bit shift value from the associated private_value, but it extracts too much; the current code extracts 8 bit values in bits 8-15, but this is a combination of two nibbles (bits 8-11 and bits 12-15) for left and right shifts. Due to the incorrect bits extraction, the actual shift may go beyond the 32bit value, as spotted recently by UBSAN check: UBSAN: Undefined behaviour in sound/pci/ac97/ac97_codec.c:836:7 shift exponent 68 is too large for 32-bit type 'int'
This patch fixes the shift value extraction by masking the properly with 0x0f instead of 0xff.
Reported-and-tested-by: Meelis Roos mroos@linux.ee Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/pci/ac97/ac97_codec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/sound/pci/ac97/ac97_codec.c +++ b/sound/pci/ac97/ac97_codec.c @@ -829,7 +829,7 @@ static int snd_ac97_put_spsa(struct snd_ { struct snd_ac97 *ac97 = snd_kcontrol_chip(kcontrol); int reg = kcontrol->private_value & 0xff; - int shift = (kcontrol->private_value >> 8) & 0xff; + int shift = (kcontrol->private_value >> 8) & 0x0f; int mask = (kcontrol->private_value >> 16) & 0xff; // int invert = (kcontrol->private_value >> 24) & 0xff; unsigned short value, old, new;