linux-kernel - [PATCH] signal/x86: Don't send SIGSEGV twice on SEGV

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Message-Id: <20210601085203.40214-1-liangjs@pku.edu.cn>
Date:   Tue,  1 Jun 2021 16:52:03 +0800
From:   Jiashuo Liang <liangjs@....edu.cn>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, Jiashuo Liang <liangjs@....edu.cn>
Subject: [PATCH] signal/x86: Don't send SIGSEGV twice on SEGV_PKUERR

Before this patch, the __bad_area_nosemaphore function calls both
force_sig_pkuerr and force_sig_fault when handling SEGV_PKUERR. This does
not cause problems because the second signal is filtered by the
legacy_queue check in __send_signal. But it causes the kernel to do
unnecessary work.

This patch should fix it.

Fixes: 9db812dbb29d ("signal/x86: Call force_sig_pkuerr from __bad_area_nosemaphore")
Suggested-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Jiashuo Liang <liangjs@....edu.cn>
---
 arch/x86/mm/fault.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 1c548ad00752..6bda7f67d737 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -836,8 +836,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 
 	if (si_code == SEGV_PKUERR)
 		force_sig_pkuerr((void __user *)address, pkey);
-
-	force_sig_fault(SIGSEGV, si_code, (void __user *)address);
+	else
+		force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 
 	local_irq_disable();
 }
-- 
2.31.1