linux-kernel - [tip: x86/urgent] x86/fault: Don't send SIGSEGV twice on SEGV

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Message-ID: <162281321853.29796.18130084021269864131.tip-bot2@tip-bot2>
Date:   Fri, 04 Jun 2021 13:26:58 -0000
From:   "tip-bot2 for Jiashuo Liang" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Jiashuo Liang <liangjs@....edu.cn>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/fault: Don't send SIGSEGV twice on SEGV_PKUERR

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     5405b42c2f08efe67b531799ba2fdb35bac93e70
Gitweb:        https://git.kernel.org/tip/5405b42c2f08efe67b531799ba2fdb35bac93e70
Author:        Jiashuo Liang <liangjs@....edu.cn>
AuthorDate:    Tue, 01 Jun 2021 16:52:03 +08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Fri, 04 Jun 2021 15:23:28 +02:00

x86/fault: Don't send SIGSEGV twice on SEGV_PKUERR

__bad_area_nosemaphore() 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() because in both cases, the signal is SIGSEGV,
the second one seeing that the first one is already pending.

This causes the kernel to do unnecessary work so send the signal only
once for SEGV_PKUERR.

 [ bp: Massage commit message. ]

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>
Signed-off-by: Borislav Petkov <bp@...e.de>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Link: https://lkml.kernel.org/r/20210601085203.40214-1-liangjs@pku.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 1c548ad..6bda7f6 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();
 }