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firmware: cs_dsp: Don't allow writes to read-only controls

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Add a check to cs_dsp_coeff_write_ctrl() to abort if the control
is not writeable.

The cs_dsp code originated as an ASoC driver (wm_adsp) where all
controls were exported as ALSA controls. It relied on ALSA to
enforce the read-only permission. Now that the code has been
separated from ALSA/ASoC it must perform its own permission check.

This isn't currently causing any problems so there shouldn't be any
need to backport this. If the client of cs_dsp exposes the control as
an ALSA control, it should set permissions on that ALSA control to
protect it. The few uses of cs_dsp_coeff_write_ctrl() inside drivers
are for writable controls.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20240702110809.16836-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Richard Fitzgerald 2024-07-02 12:08:09 +01:00 committed by Mark Brown
parent a893a804c6
commit 62412a9357
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GPG Key ID: 24D68B725D5487D0
1 changed files with 3 additions and 0 deletions
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3
drivers/firmware/cirrus/cs_dsp.c
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@ -796,6 +796,9 @@ int cs_dsp_coeff_write_ctrl(struct cs_dsp_coeff_ctl *ctl,
lockdep_assert_held(&ctl->dsp->pwr_lock);
if (ctl->flags && !(ctl->flags & WMFW_CTL_FLAG_WRITEABLE))
return -EPERM;
if (len + off * sizeof(u32) > ctl->len)
return -EINVAL;