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Wed, 02 Nov 2022 04:06:26 -0700 (PDT) Date: Wed, 2 Nov 2022 12:06:11 +0100 In-Reply-To: <20221102110611.1085175-1-glider@google.com> Mime-Version: 1.0 References: <20221102110611.1085175-1-glider@google.com> X-Mailer: git-send-email 2.38.1.273.g43a17bfeac-goog Message-ID: <20221102110611.1085175-5-glider@google.com> Subject: [PATCH 5/5] x86/traps: avoid KMSAN bugs originating from handle_bug() From: Alexander Potapenko To: glider@google.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Borislav Petkov , Dave Hansen , Ingo Molnar , Thomas Gleixner , x86@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667387188; a=rsa-sha256; cv=none; b=lcsUAy07eLlZ3ropY8xXPGvA7zUG2inWqhA+lbdjnJIDLX/qmau+K8JihOii8KDjglK4pg ewwIZ189dK80G5FTwQy2Zs7mKiJgwckH7eAJYUf+eKLhrQ9+L2taamW9b33ATSzrf07UHN fYXpWBgG66FjJ5En7p7IHd0RHNnY7kI= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=BRXuAvLO; spf=pass (imf25.hostedemail.com: domain of 3Mk9iYwYKCHsfkhcdqfnnfkd.bnlkhmtw-lljuZbj.nqf@flex--glider.bounces.google.com designates 209.85.208.74 as permitted sender) smtp.mailfrom=3Mk9iYwYKCHsfkhcdqfnnfkd.bnlkhmtw-lljuZbj.nqf@flex--glider.bounces.google.com; 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dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1667387187-669485 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: There is a case in exc_invalid_op handler that is executed outside the irqentry_enter()/irqentry_exit() region when an UD2 instruction is used to encode a call to __warn(). In that case the `struct pt_regs` passed to the interrupt handler is never unpoisoned by KMSAN (this is normally done in irqentry_enter()), which leads to false positives inside handle_bug(). Use kmsan_unpoison_entry_regs() to explicitly unpoison those registers before using them. Cc: Andrew Morton Cc: Borislav Petkov Cc: Dave Hansen Cc: Ingo Molnar Cc: Thomas Gleixner Cc: x86@kernel.org Signed-off-by: Alexander Potapenko --- arch/x86/kernel/traps.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 178015a820f08..d3fdec706f1d2 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -301,6 +302,12 @@ static noinstr bool handle_bug(struct pt_regs *regs) { bool handled = false; + /* + * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug() + * is a rare case that uses @regs without passing them to + * irqentry_enter(). + */ + kmsan_unpoison_entry_regs(regs); if (!is_valid_bugaddr(regs->ip)) return handled;