linux-kernel - [PATCH v2 1/2] x86/arch_prctl: Fix the ARCH_REQ_XCOMP

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Message-Id: <20211109012122.1142-2-chang.seok.bae@intel.com>
Date:   Mon,  8 Nov 2021 17:21:21 -0800
From:   "Chang S. Bae" <chang.seok.bae@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, tglx@...utronix.de, dave.hansen@...ux.intel.com,
        bp@...en8.de, mingo@...hat.com, yang.zhong@...el.com,
        jing2.liu@...el.com, chang.seok.bae@...el.com
Subject: [PATCH v2 1/2] x86/arch_prctl: Fix the ARCH_REQ_XCOMP_PERM implementation

ARCH_REQ_XCOMP_PERM is supposed to add the requested feature to the
permission bitmap of thread_group_leader()->fpu. But the code overwrites
the bitmap with the requested feature bit only rather than adding it.

Fix the code to add the request feature bit to the master bitmask.

Reported-by: Yang Zhong <yang.zhong@...el.com>
Fixes: db8268df0983 ("x86/arch_prctl: Add controls for dynamic XSTATE components")
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
Changes from v1:
* Change the mask value only and trim the changelog.
---
 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;
-- 
2.17.1