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 B1B89247287; Tue, 12 Aug 2025 18:50:08 +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=1755024608; cv=none; b=XyEeX3jkKPbv96uhsvf6ZuATSNC/3SgQt7BqkwOM9ii/sVnCXzR8uu4dTPUNLPz9esJLVk10efUIJuBQw4goBmCFcOhkVYZJMyV1Nsgg0CNXVd6n8BiERKg+l0LgJUfmVwjAa+AMl2huqRq0rH1tZxpQFMPe00hd+u+M/7Ij+wo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755024608; c=relaxed/simple; bh=sMQXHvvv4n8Z0bUxsV8/AQdzJAIedTV2xSrDTLpmgjI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iKIdpfRuQAXqccVLV2U6xMUhzCuqQKq6p4DDJfcVK8Mecvsd7AM6TMZlceU52u1ISfA087YxJmG018K7mlkdmYDFHQ/9Km/wjQ0j1q49UpPxUFMRDaqmgn4GGYb7R3s8kxExscZvSpLOujKVB8mDFHH1dZNM+wSSxteGXghd7G4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=jTeww/Ye; 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="jTeww/Ye" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E4E98C4CEF0; Tue, 12 Aug 2025 18:50:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755024608; bh=sMQXHvvv4n8Z0bUxsV8/AQdzJAIedTV2xSrDTLpmgjI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jTeww/YeB25nL1MVMW9+JdBYOq03zlmDGk8J2TPbQfstOI8TRbkCmF7sY/ZhIIF9j +qhpuVWBN/iZcf72kOli5nuPxX2nKvtwc5h1IYRlgCENpUpF7e0GwAvqR053KQuCdr J8Xk5yfhmz7vQsQ4b1O19at2rEP4pmBNRf51blBs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mukesh Ojha , Linus Walleij , Sasha Levin Subject: [PATCH 6.16 380/627] pinmux: fix race causing mux_owner NULL with active mux_usecount Date: Tue, 12 Aug 2025 19:31:15 +0200 Message-ID: <20250812173433.752838160@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250812173419.303046420@linuxfoundation.org> References: <20250812173419.303046420@linuxfoundation.org> User-Agent: quilt/0.68 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 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mukesh Ojha [ Upstream commit 0b075c011032f88d1cfde3b45d6dcf08b44140eb ] commit 5a3e85c3c397 ("pinmux: Use sequential access to access desc->pinmux data") tried to address the issue when two client of the same gpio calls pinctrl_select_state() for the same functionality, was resulting in NULL pointer issue while accessing desc->mux_owner. However, issue was not completely fixed due to the way it was handled and it can still result in the same NULL pointer. The issue occurs due to the following interleaving: cpu0 (process A) cpu1 (process B) pin_request() { pin_free() { mutex_lock() desc->mux_usecount--; //becomes 0 .. mutex_unlock() mutex_lock(desc->mux) desc->mux_usecount++; // becomes 1 desc->mux_owner = owner; mutex_unlock(desc->mux) mutex_lock(desc->mux) desc->mux_owner = NULL; mutex_unlock(desc->mux) This sequence leads to a state where the pin appears to be in use (`mux_usecount == 1`) but has no owner (`mux_owner == NULL`), which can cause NULL pointer on next pin_request on the same pin. Ensure that updates to mux_usecount and mux_owner are performed atomically under the same lock. Only clear mux_owner when mux_usecount reaches zero and no new owner has been assigned. Fixes: 5a3e85c3c397 ("pinmux: Use sequential access to access desc->pinmux data") Signed-off-by: Mukesh Ojha Link: https://lore.kernel.org/20250708-pinmux-race-fix-v2-1-8ae9e8a0d1a1@oss.qualcomm.com Signed-off-by: Linus Walleij Signed-off-by: Sasha Levin --- drivers/pinctrl/pinmux.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c index 0743190da59e..2c31e7f2a27a 100644 --- a/drivers/pinctrl/pinmux.c +++ b/drivers/pinctrl/pinmux.c @@ -236,18 +236,7 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin, if (desc->mux_usecount) return NULL; } - } - - /* - * If there is no kind of request function for the pin we just assume - * we got it by default and proceed. - */ - if (gpio_range && ops->gpio_disable_free) - ops->gpio_disable_free(pctldev, gpio_range, pin); - else if (ops->free) - ops->free(pctldev, pin); - scoped_guard(mutex, &desc->mux_lock) { if (gpio_range) { owner = desc->gpio_owner; desc->gpio_owner = NULL; @@ -258,6 +247,15 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin, } } + /* + * If there is no kind of request function for the pin we just assume + * we got it by default and proceed. + */ + if (gpio_range && ops->gpio_disable_free) + ops->gpio_disable_free(pctldev, gpio_range, pin); + else if (ops->free) + ops->free(pctldev, pin); + module_put(pctldev->owner); return owner; -- 2.39.5