linux-kernel - [PATCH] x86/fpu: Set the corret permission value for perm.__state

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Message-Id: <20211108222815.4078-1-yang.zhong@intel.com>
Date:   Mon,  8 Nov 2021 17:28:15 -0500
From:   Yang Zhong <yang.zhong@...el.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     tglx@...utronix.de, bp@...e.de, dave.hansen@...el.com,
        chang.seok.bae@...el.com, yang.zhong@...el.com, jing2.liu@...el.com
Subject: [PATCH] x86/fpu: Set the corret permission value for perm.__state_perm

The perm.__state_perm is default xsave set features, when we request
AMX permission from application, the requested value(bit18) should be
replaced with mask value(requested | permitted), which can keep default
features there.

Without this change, the below prctl syscall:
(1). ARCH_GET_XCOMP_PERM, the bitmask=0x202e7
(2). set ARCH_REQ_XCOMP_PERM with XFEATURE_XTILEDATA
(3). ARCH_GET_XCOMP_PERM, the bitmask=0x40000, the correct value
     should be 0x602e7 here.

Signed-off-by: Yang Zhong <yang.zhong@...el.com>
---
 arch/x86/kernel/fpu/xstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index d28829403ed0..fc1ab0116f4e 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1626,7 +1626,7 @@ static int __xstate_request_perm(u64 permitted, u64 requested)
 		return ret;
 
 	/* Pairs with the READ_ONCE() in xstate_get_group_perm() */
-	WRITE_ONCE(fpu->perm.__state_perm, requested);
+	WRITE_ONCE(fpu->perm.__state_perm, mask);
 	/* Protected by sighand lock */
 	fpu->perm.__state_size = ksize;
 	fpu->perm.__user_state_size = usize;
-- 
2.30.2