linux-kernel - [PATCH] x86: math-emu: fix div

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250807205334.123231-1-arnd@kernel.org>
Date: Thu,  7 Aug 2025 22:53:28 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Bill Metzenthen <billm@...bpc.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] x86: math-emu: fix div_Xsig prototype

From: Arnd Bergmann <arnd@...db.de>

The third argument of div_Xsig() is the output of the division, but is marked
'const', which means the compiler is not expecting it to be updated and may
generate bad code around the call. clang-21 now warns about the pattern since
an uninitialized variable is passed into two 'const' arguments by reference:

arch/x86/math-emu/poly_atan.c:93:28: error: variable 'argSignif' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
   93 |         div_Xsig(&Numer, &Denom, &argSignif);
      |                                   ^~~~~~~~~
arch/x86/math-emu/poly_l2.c:195:29: error: variable 'argSignif' is uninitialized when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
  195 |                 div_Xsig(&Numer, &Denom, &argSignif);
      |                                           ^~~~~~~~~

The implementation is in assembly, so the problem has gone unnoticed since the
code was added in the linux-1.1 days. Remove the 'const' marker here.

Fixes: e19a1bdb835c ("Import 1.1.38")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/math-emu/poly.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/math-emu/poly.h b/arch/x86/math-emu/poly.h
index fc1c887ca073..654bfe4e29a0 100644
--- a/arch/x86/math-emu/poly.h
+++ b/arch/x86/math-emu/poly.h
@@ -39,7 +39,7 @@ asmlinkage void mul_Xsig_Xsig(Xsig *dest, const Xsig *mult);
 asmlinkage void shr_Xsig(Xsig *, const int n);
 asmlinkage int round_Xsig(Xsig *);
 asmlinkage int norm_Xsig(Xsig *);
-asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, const Xsig *dest);
+asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, Xsig *dest);
 
 /* Macro to extract the most significant 32 bits from a long long */
 #define LL_MSW(x)     (((unsigned long *)&x)[1])
-- 
2.39.5