[PATCH] ALSA: asihpi: work around clang-17+ false positive fortify-string warning

From: Arnd Bergmann <arnd@kernel.org>
To: Kees Cook <keescook@chromium.org>,
	Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev
Subject: [PATCH] ALSA: asihpi: work around clang-17+ false positive fortify-string warning
Date: Wed, 28 Feb 2024 15:01:45 +0100	[thread overview]
Message-ID: <20240228140152.1824901-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

One of the memory copies in this driver triggers a warning about a
possible out of range access:

In file included from /home/arnd/arm-soc/sound/pci/asihpi/hpimsgx.c:13:
/home/arnd/arm-soc/include/linux/fortify-string.h:553:4: error: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
  553 |                         __write_overflow_field(p_size_field, size);
      |                         ^

Adding a range check avoids the problem, though I don't quite see
why it warns in the first place if clang has no knowledge of the
actual range of the type, or why I never saw the warning in previous
randconfig tests.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 sound/pci/asihpi/hpimsgx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/pci/asihpi/hpimsgx.c b/sound/pci/asihpi/hpimsgx.c
index d0caef299481..4f245c3956b1 100644
--- a/sound/pci/asihpi/hpimsgx.c
+++ b/sound/pci/asihpi/hpimsgx.c
@@ -576,6 +576,9 @@ static u16 adapter_prepare(u16 adapter)
 	/* Open the adapter and streams */
 	u16 i;
 
+	if (adapter >= ARRAY_SIZE(rESP_HPI_ADAPTER_OPEN))
+		return 0;
+
 	/* call to HPI_ADAPTER_OPEN */
 	hpi_init_message_response(&hm, &hr, HPI_OBJ_ADAPTER,
 		HPI_ADAPTER_OPEN);
-- 
2.39.2

