| Message ID | 20250310222249.work.154-kees@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | wireguard: noise: Add __nonstring annotations for unterminated strings | expand |
On Mon, 10 Mar 2025 15:22:50 -0700 Kees Cook wrote: > When a character array without a terminating NUL character has a static > initializer, GCC 15's -Wunterminated-string-initialization will only > warn if the array lacks the "nonstring" attribute[1]. Mark the arrays > with __nonstring to and correctly identify the char array as "not a C > string" and thereby eliminate the warning. Hi! Would marking all of u8 as non-string not be an option? How many of such warnings do we have in the tree? Feel free to point me to a previous conversation.
On Tue, Mar 11, 2025 at 11:19:27AM +0100, Jakub Kicinski wrote: > On Mon, 10 Mar 2025 15:22:50 -0700 Kees Cook wrote: > > When a character array without a terminating NUL character has a static > > initializer, GCC 15's -Wunterminated-string-initialization will only > > warn if the array lacks the "nonstring" attribute[1]. Mark the arrays > > with __nonstring to and correctly identify the char array as "not a C > > string" and thereby eliminate the warning. > > Hi! Would marking all of u8 as non-string not be an option? How many > of such warnings do we have in the tree? Feel free to point me to a > previous conversation. *thread merge* On Mon, Mar 10, 2025 at 06:38:01PM -0400, James Bottomley wrote[1]: > This looks a bit suboptimal ... is there anywhere in the kernel u8[] is > actually used for real strings? In which case it would seem the better > place to put the annotation is in the typedef for u8 arrays. So both of you asked basically same question, and I think the simple answer is "no we can't mark u8 as nonstring". The use of u8 has become synonymous with "char" for a long while now, and it's gotten even more common after we made char unsigned by default. The number of warning sources is pretty small. I think I have identified and proposed fixes most of them already[2]. ACPICA needs an upstream change, which I've submitted[3]. And ACPI needed multidimensional nonstring annotation support, which had the last needed bit added to GCC today[4], and I've proposed support for it in the kernel[5]. With 4 and 5 ready, I can send the final patch, which is basically just this (and actually accounts for the vast majority of warnings emitted): -static const char table_sigs[][ACPI_NAMESEG_SIZE] __initconst = { +static const char table_sigs[][ACPI_NAMESEG_SIZE] __nonstring_array __initconst = { -Kees [1] https://lore.kernel.org/lkml/98ca3727d65a418e403b03f6b17341dbcb192764.camel@HansenPartnership.com/ [2] https://lore.kernel.org/lkml/?q=f%3AKees+%22-Wunterminated-string-initialization%22 [3] https://github.com/acpica/acpica/pull/1006 [4] https://github.com/gcc-mirror/gcc/commit/afb46540d3921e96c4cd7ba8fa2c8b0901759455 [5] https://lore.kernel.org/lkml/20250310214244.work.194-kees@kernel.org/
diff --git a/drivers/net/wireguard/noise.c b/drivers/net/wireguard/noise.c index 202a33af5a72..7eb9a23a3d4d 100644 --- a/drivers/net/wireguard/noise.c +++ b/drivers/net/wireguard/noise.c @@ -25,8 +25,8 @@ * <- e, ee, se, psk, {} */ -static const u8 handshake_name[37] = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s"; -static const u8 identifier_name[34] = "WireGuard v1 zx2c4 Jason@zx2c4.com"; +static const u8 handshake_name[37] __nonstring = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s"; +static const u8 identifier_name[34] __nonstring = "WireGuard v1 zx2c4 Jason@zx2c4.com"; static u8 handshake_init_hash[NOISE_HASH_LEN] __ro_after_init; static u8 handshake_init_chaining_key[NOISE_HASH_LEN] __ro_after_init; static atomic64_t keypair_counter = ATOMIC64_INIT(0);
When a character array without a terminating NUL character has a static initializer, GCC 15's -Wunterminated-string-initialization will only warn if the array lacks the "nonstring" attribute[1]. Mark the arrays with __nonstring to and correctly identify the char array as "not a C string" and thereby eliminate the warning. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1] Cc: Jason A. Donenfeld <Jason@zx2c4.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Andrew Lunn <andrew+netdev@lunn.ch> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: wireguard@lists.zx2c4.com Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook <kees@kernel.org> --- drivers/net/wireguard/noise.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)