From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DED74280327; Thu, 15 Jan 2026 17:16:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768497378; cv=none; b=FuuBEGdAvLrDHgbd+qjZV5dmv0Eq2ikfwYoVcO4i34MD3HNcG8x+RR1grEmBJjLFkp+cLSSKKrVP8iij2ukDaCd9UNhIvqhhQA6yE5ovtiEtKbncH/+QfQ5Id75LCgvbt65qojs9k9TftEGsuzSpeOIO9McX/itVpS92tYFaJxQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768497378; c=relaxed/simple; bh=DFSzto33tx0Ev7UOYy/CE5TcMeyoosOWyPVBvW0+pc4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aeLFWiJz35ht+lsM7bo5CS8e5otyjV6YMWcD9+tpR1/m0Ge1gQ9d/PrzLhUMngIN5dd9bySPQ1/G5Ehh87N2Y5vD1SrEl1itZDpAi6QaJ6k5JPc7sWKbLDquUGl5wWZwmDzgZaTWro7Tw+8UQFWiaj9oSyVJo86/kQG4NZwSDYg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=e5opy4Lb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="e5opy4Lb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40D1AC116D0; Thu, 15 Jan 2026 17:16:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1768497378; bh=DFSzto33tx0Ev7UOYy/CE5TcMeyoosOWyPVBvW0+pc4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=e5opy4Lb4PK0KAporcu9RkeI7jejHjv2epaVOPLvnfA38G3bkzagmWJK6h+k8ZWAT BNcGLTZq+N7NzALsvwubNmLE2a24uAq+yTXgBcD282wQLl096W8P7mDH3ZTR94QzMz uCANycsW/VXH6NjKORhG7q+O31rjZmx4yeSFF5F0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexander Potapenko , Alexander Viro , Alexei Starovoitov , Andrey Konovalov , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Biggers , Eric Biggers , Eric Dumazet , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Stephen Rothwell , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , Andrew Morton , Sasha Levin Subject: [PATCH 5.15 059/554] x86: kmsan: dont instrument stack walking functions Date: Thu, 15 Jan 2026 17:42:05 +0100 Message-ID: <20260115164248.382514922@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260115164246.225995385@linuxfoundation.org> References: <20260115164246.225995385@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Potapenko [ Upstream commit 37ad4ee8364255c73026a3c343403b5977fa7e79 ] Upon function exit, KMSAN marks local variables as uninitialized. Further function calls may result in the compiler creating the stack frame where these local variables resided. This results in frame pointers being marked as uninitialized data, which is normally correct, because they are not stack-allocated. However stack unwinding functions are supposed to read and dereference the frame pointers, in which case KMSAN might be reporting uses of uninitialized values. To work around that, we mark update_stack_state(), unwind_next_frame() and show_trace_log_lvl() with __no_kmsan_checks, preventing all KMSAN reports inside those functions and making them return initialized values. Link: https://lkml.kernel.org/r/20220915150417.722975-40-glider@google.com Signed-off-by: Alexander Potapenko Cc: Alexander Viro Cc: Alexei Starovoitov Cc: Andrey Konovalov Cc: Andrey Konovalov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Christoph Hellwig Cc: Christoph Lameter Cc: David Rientjes Cc: Dmitry Vyukov Cc: Eric Biggers Cc: Eric Biggers Cc: Eric Dumazet Cc: Greg Kroah-Hartman Cc: Herbert Xu Cc: Ilya Leoshkevich Cc: Ingo Molnar Cc: Jens Axboe Cc: Joonsoo Kim Cc: Kees Cook Cc: Marco Elver Cc: Mark Rutland Cc: Matthew Wilcox Cc: Michael S. Tsirkin Cc: Pekka Enberg Cc: Peter Zijlstra Cc: Petr Mladek Cc: Stephen Rothwell Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vegard Nossum Cc: Vlastimil Babka Signed-off-by: Andrew Morton Stable-dep-of: ced37e9ceae5 ("x86/dumpstack: Prevent KASAN false positive warnings in __show_regs()") Signed-off-by: Sasha Levin --- arch/x86/kernel/dumpstack.c | 6 ++++++ arch/x86/kernel/unwind_frame.c | 11 +++++++++++ 2 files changed, 17 insertions(+) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 8a8660074284f..4adbc85b74a33 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -183,6 +183,12 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs, } } +/* + * This function reads pointers from the stack and dereferences them. The + * pointers may not have their KMSAN shadow set up properly, which may result + * in false positive reports. Disable instrumentation to avoid those. + */ +__no_kmsan_checks static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, unsigned long *stack, const char *log_lvl) { diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index d7c44b257f7f4..8943114f9ebed 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -183,6 +183,16 @@ static struct pt_regs *decode_frame_pointer(unsigned long *bp) } #endif +/* + * While walking the stack, KMSAN may stomp on stale locals from other + * functions that were marked as uninitialized upon function exit, and + * now hold the call frame information for the current function (e.g. the frame + * pointer). Because KMSAN does not specifically mark call frames as + * initialized, false positive reports are possible. To prevent such reports, + * we mark the functions scanning the stack (here and below) with + * __no_kmsan_checks. + */ +__no_kmsan_checks static bool update_stack_state(struct unwind_state *state, unsigned long *next_bp) { @@ -251,6 +261,7 @@ static bool update_stack_state(struct unwind_state *state, return true; } +__no_kmsan_checks bool unwind_next_frame(struct unwind_state *state) { struct pt_regs *regs; -- 2.51.0