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 3248B319611; Mon, 13 Oct 2025 15:28:13 +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=1760369293; cv=none; b=ZQhwScit/O/ntCmegG54hORibtoke2kbkH0xv0UhkmZ/8YCiBOZH2WMXL52H8aR25reLu9Z//vROGVHP/uYNRO/g3Q84wSLOqa6Un3UR1WZ47bl/fPxljikyOyE+GirYn9er5x3XZKp13fpCQCyK099OcYoiNeapDuSC8GjxWhA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760369293; c=relaxed/simple; bh=sWcVLhs3OYus4UZrC3M3Qddip2QGBtIy3h58Z8LHEqI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CoQLmrCi1x4dyMiDAZxThnf6lBqd24PO8haXXfrwBAa7goyK49iQ4ldIEgpQgt2R9I+8Xxqob3P6Sa0LbicaoZGf0I5dInvJtmM0x5upPviU5fMGhrTayKjj2j8KO5iE3Nnjb6i7LEWSUhknP3/aEiw6PQtjlRju7urGqRBrXns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=z4f9MKmy; 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="z4f9MKmy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC996C116B1; Mon, 13 Oct 2025 15:28:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760369293; bh=sWcVLhs3OYus4UZrC3M3Qddip2QGBtIy3h58Z8LHEqI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=z4f9MKmyy8SmD6bIvrxHn2L3AzWuhFt1OJWasxX4NPGAq0yEn5iix1OiwHjUcbpG+ LrlE3nQiLHB862xcx7YNPBYsyvLUIoCRlI8sz9+myDIF4jS2z5IZwYPXfh3pS4/aWW Fv+oF9gB9ngt4COISMb2bk1cSjA4/VRKsZUulCOs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hulk Robot , Qi Xi , Arnd Bergmann , Sasha Levin Subject: [PATCH 6.17 194/563] once: fix race by moving DO_ONCE to separate section Date: Mon, 13 Oct 2025 16:40:55 +0200 Message-ID: <20251013144418.310115483@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013144411.274874080@linuxfoundation.org> References: <20251013144411.274874080@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qi Xi [ Upstream commit edcc8a38b5ac1a3dbd05e113a38a25b937ebefe5 ] The commit c2c60ea37e5b ("once: use __section(".data.once")") moved DO_ONCE's ___done variable to .data.once section, which conflicts with DO_ONCE_LITE() that also uses the same section. This creates a race condition when clear_warn_once is used: Thread 1 (DO_ONCE) Thread 2 (DO_ONCE) __do_once_start read ___done (false) acquire once_lock execute func __do_once_done write ___done (true) __do_once_start release once_lock // Thread 3 clear_warn_once reset ___done read ___done (false) acquire once_lock execute func schedule once_work __do_once_done once_deferred: OK write ___done (true) static_branch_disable release once_lock schedule once_work once_deferred: BUG_ON(!static_key_enabled) DO_ONCE_LITE() in once_lite.h is used by WARN_ON_ONCE() and other warning macros. Keep its ___done flag in the .data..once section and allow resetting by clear_warn_once, as originally intended. In contrast, DO_ONCE() is used for functions like get_random_once() and relies on its ___done flag for internal synchronization. We should not reset DO_ONCE() by clear_warn_once. Fix it by isolating DO_ONCE's ___done into a separate .data..do_once section, shielding it from clear_warn_once. Fixes: c2c60ea37e5b ("once: use __section(".data.once")") Reported-by: Hulk Robot Signed-off-by: Qi Xi Signed-off-by: Arnd Bergmann Signed-off-by: Sasha Levin --- include/asm-generic/vmlinux.lds.h | 1 + include/linux/once.h | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index ae2d2359b79e9..8efbe8c4874ee 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -361,6 +361,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) __start_once = .; \ *(.data..once) \ __end_once = .; \ + *(.data..do_once) \ STRUCT_ALIGN(); \ *(__tracepoints) \ /* implement dynamic printk debug */ \ diff --git a/include/linux/once.h b/include/linux/once.h index 30346fcdc7995..449a0e34ad5ad 100644 --- a/include/linux/once.h +++ b/include/linux/once.h @@ -46,7 +46,7 @@ void __do_once_sleepable_done(bool *done, struct static_key_true *once_key, #define DO_ONCE(func, ...) \ ({ \ bool ___ret = false; \ - static bool __section(".data..once") ___done = false; \ + static bool __section(".data..do_once") ___done = false; \ static DEFINE_STATIC_KEY_TRUE(___once_key); \ if (static_branch_unlikely(&___once_key)) { \ unsigned long ___flags; \ @@ -64,7 +64,7 @@ void __do_once_sleepable_done(bool *done, struct static_key_true *once_key, #define DO_ONCE_SLEEPABLE(func, ...) \ ({ \ bool ___ret = false; \ - static bool __section(".data..once") ___done = false; \ + static bool __section(".data..do_once") ___done = false; \ static DEFINE_STATIC_KEY_TRUE(___once_key); \ if (static_branch_unlikely(&___once_key)) { \ ___ret = __do_once_sleepable_start(&___done); \ -- 2.51.0