[PATCH] ASoC: cs-amp-lib: Prevent NULL pointer if efi variable is zero length

[PATCH] ASoC: cs-amp-lib: Prevent NULL pointer if efi variable is zero length

[Richard Fitzgerald]

In cs_amp_alloc_get_efi_variable() the first call to
cs_amp_get_efi_variable() might return EFI_SUCCESS if the variable
exists with zero length. Trap this and return -ENOENT to prevent
returning an unexpected NULL pointer.

The first cs_amp_get_efi_variable() call was assumed to return
EFI_BUFFER_TOO_SMALL if the variable existed, but if instead it
returned EFI_SUCCESS this would be converted to 0 by
cs_amp_convert_efi_status() and then be returned as a NULL pointer.

Fixes: 00fd40bc7acec ("ASoC: cs-amp-lib: Support Dell SSIDExV2 UEFI variable")
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 sound/soc/codecs/cs-amp-lib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/soc/codecs/cs-amp-lib.c b/sound/soc/codecs/cs-amp-lib.c
index 41a9a5b005c63..9bc19d2e16394 100644
--- a/sound/soc/codecs/cs-amp-lib.c
+++ b/sound/soc/codecs/cs-amp-lib.c
@@ -317,6 +317,8 @@ static void *cs_amp_alloc_get_efi_variable(efi_char16_t *name,
 	unsigned long size = 0;
 
 	status = cs_amp_get_efi_variable(name, guid, NULL, &size, NULL);
+	if (status == EFI_SUCCESS)
+		return ERR_PTR(-ENOENT);
 	if (status != EFI_BUFFER_TOO_SMALL)
 		return ERR_PTR(cs_amp_convert_efi_status(status));
 
-- 
2.47.3

Re: [PATCH] ASoC: cs-amp-lib: Prevent NULL pointer if efi variable is zero length

[Mark Brown]

On Mon, 14 Sep 2026 13:26:11 +0100, Richard Fitzgerald wrote:
> ASoC: cs-amp-lib: Prevent NULL pointer if efi variable is zero length

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.3

Thanks!

[1/1] ASoC: cs-amp-lib: Prevent NULL pointer if efi variable is zero length
      https://git.kernel.org/broonie/sound/c/8ffd16d6875e

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark