linux-kernel - [PATCH] x86/fpu: remove memset call for xmm registers on xfpregs

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Date:   Tue, 25 Jan 2022 02:20:15 +0000
From:   Luís Ferreira <contact@...erreira.net>
To:     linux-kernel@...r.kernel.org
Cc:     bp@...en8.de,
        Luís Ferreira <contact@...erreira.net>
Subject: [PATCH] x86/fpu: remove memset call for xmm registers on xfpregs_set

This patch fixes https://bugzilla.kernel.org/show_bug.cgi?id=215524 by removing
the memset introduced by 6164331d15f7d912fb9369245368e9564ea49813, which
created a regression on ptrace PTRACE_SETREGSET request with NT_FPREGSET.
Particularly, it zeros some XMM registers on the wrong offsets. Fixing the offsets
only solves the problem for i686, which doesn't include xmm8-15 registers, so
the right way is to probably completely remove this call.

Signed-off-by: Luís Ferreira <contact@...erreira.net>
---
 arch/x86/kernel/fpu/regset.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index 437d7c930c0b..aec6c49029b1 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -116,9 +116,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 	/* Copy the state  */
 	memcpy(&fpu->fpstate->regs.fxsave, &newstate, sizeof(newstate));

-	/* Clear xmm8..15 */
 	BUILD_BUG_ON(sizeof(fpu->__fpstate.regs.fxsave.xmm_space) != 16 * 16);
-	memset(&fpu->fpstate->regs.fxsave.xmm_space[8], 0, 8 * 16);

 	/* Mark FP and SSE as in use when XSAVE is enabled */
 	if (use_xsave())
-- 
2.34.1