Re: [PATCH v3] ASoC: fsl_sai: Fix 32 slots TDM broken by integer shift UB in xMR write
From: Shengjiu Wang <shengjiu.wang@gmail.com>
Date: 2026-06-04 09:37:20
Also in:
linux-sound, lkml, stable
On Mon, Jun 1, 2026 at 4:33 PM [off-list ref] wrote:
From: Chancel Liu <redacted>
When configuring 32 slots TDM (channels == slots == 32), the xMR
(Mask Register) write used:
~0UL - ((1 << min(channels, slots)) - 1)
The literal "1" is a signed 32-bit int. Shifting it by 32 positions is
undefined behaviour which may set this register to 0xFFFFFFFF, masking
all 32 slots.
Use GENMASK_U32() macro instead. For 32 slots this produces a zero mask:
~GENMASK_U32(31, 0) = ~0xFFFFFFFF = 0x00000000
Behaviour for fewer than 32 slots is unchanged.
Fixes: 770f58d7d2c5 ("ASoC: fsl_sai: Support multiple data channel enable bits")
Cc: stable@vger.kernel.org
Signed-off-by: Chancel Liu <redacted>Reviewed-by: Shengjiu Wang <shengjiu.wang@gmail.com> Best regards Shengjiu Wang
quoted hunk ↗ jump to hunk
--- Changes in v3 - Fix patch can't be applied Changes in v2 - Use GENMASK_U32() macro instead to make it clearer and safer sound/soc/fsl/fsl_sai.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c index d6dd95680892..9661602b53c5 100644 --- a/sound/soc/fsl/fsl_sai.c +++ b/sound/soc/fsl/fsl_sai.c@@ -797,7 +797,7 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream, FSL_SAI_CR4_FSD_MSTR, FSL_SAI_CR4_FSD_MSTR); regmap_write(sai->regmap, FSL_SAI_xMR(tx), - ~0UL - ((1 << min(channels, slots)) - 1)); + ~GENMASK_U32(min(channels, slots) - 1, 0)); return 0; } --2.50.1