From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793213414; b=MUOAfjSebN+DuGl9NzlyP6EQEqaHJxlkDKqco6A5QOUaqMlAx4nPgmyQwXzHeDi5kFbb 6aufPtLG2lImnkcF3ciLxVuG3fa+zN4q56OoNF/Eox1hQcdFBOhyoH158hAPNcHzqo3wB VUVM3Z6DpcwYRZz5fWgI2Q2Q0x4G2FPJC5tP5Vf9fvoP0/Et0lRetJtPAQvygo162mxPn YL0UJFUUBIpyoMuCXSlTPBP+xJnQFFfDFEuAnd5eeL+NQlcva6InLoItgJwW6BH1hT++A UG/O9v3fizlA325gFIpjfKn11DHxIA1KtIfJsi1M6kYoYBHjCOlznEQB2NthgdayZSA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793213414; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=zhV8ZhRBlHLhmquwd1lUSYQDaIaBnjr1TCFOAKZEPI4=; b=esU69W8V3pDleCYg4lGL5KBhsYicyu47WOWaAJLejdRTMqzLuv1K/rL9xpJ77DexRcPR 7d2CBpLbFKgRe0FG9Z0fTGw5/GWfgKyTZmiUy/ttMEC1iFyYSA2H0iKGBWg0nqhSvFlkI oHVbIrMuUR+k51OONsPoX05kTyxilFzDbsOIJkgyRCeE2vsyK6oEXRJbc2JbUR8n79y7/ BCKUsaz3XOZurww7qVsNUOijG5YECBZpXFHZt0o6kv2uL3nypdArJcEz9MUE41HWi0SUe tWTn8alZVaAbJrAg0uuoFUGbyc9qFIriFeNvJY+e25onqJpBetqY0Sj87zv89p64Kbw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=MbqvhFBg; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC2DB606A31A; Wed, 28 Oct 2026 18:50:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=MbqvhFBg Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2945E1F01825; Wed, 28 Oct 2026 18:50:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793213413; bh=zhV8ZhRBlHLhmquwd1lUSYQDaIaBnjr1TCFOAKZEPI4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=MbqvhFBgk3yQS5++PRQVWV8WU1sDAyZJTBwAsBRN4mSQe8FFSomtv/0D4mD3K9Cof k+7Yjoh0zrhEF3bFdpNiC/pJ0H1UG/mLnoUtE2eI5zsfPPLausyMwcut4ei9HEXloS 2tKq9UGeXEtPAWAXrkee4Pb6M5Mf6UEHXfQljO0Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tomas Winkler , Alexander Usyskin , Zhang Xiaoxu , Miquel Raynal Subject: [PATCH 6.1 0498/1887] mtd: Clean refcounting with MTD_PARTITIONED_MASTER Date: Wed, 28 Oct 2026 17:43:14 +0100 Message-ID: <20261028170510.621969547@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miquel Raynal commit 264725e35fbc3b67e053a405e022393a6017e6da upstream. The logic is way too convoluted, let's clean the kref_get/put section to clarify what this block does when using CONFIG_MTD_PARTITIONED_MASTER: - Iterate through all the parent mtd devices - Grab a reference over them all but the master - Only grab the master whith CONFIG_MTD_PARTITIONED_MASTER Same logic must apply in the put path, otherwise it would be broken. Cc: Tomas Winkler Cc: Alexander Usyskin Cc: Zhang Xiaoxu Fixes: 19bfa9ebebb5 ("mtd: use refcount to prevent corruption") Signed-off-by: Miquel Raynal Tested-by: Alexander Usyskin Link: https://lore.kernel.org/linux-mtd/20230731090903.770277-1-miquel.raynal@bootlin.com Signed-off-by: Greg Kroah-Hartman --- drivers/mtd/mtdcore.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) --- a/drivers/mtd/mtdcore.c +++ b/drivers/mtd/mtdcore.c @@ -1221,14 +1221,15 @@ int __get_mtd_device(struct mtd_info *mt return -ENODEV; } - kref_get(&mtd->refcnt); - - while (mtd->parent) { - if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) || mtd->parent != master) - kref_get(&mtd->parent->refcnt); + while (mtd) { + if (mtd != master) + kref_get(&mtd->refcnt); mtd = mtd->parent; } + if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) + kref_get(&master->refcnt); + return 0; } EXPORT_SYMBOL_GPL(__get_mtd_device); @@ -1312,10 +1313,12 @@ void __put_mtd_device(struct mtd_info *m { struct mtd_info *master = mtd_get_master(mtd); - while (mtd != master) { + while (mtd) { + /* kref_put() can relese mtd, so keep a reference mtd->parent */ struct mtd_info *parent = mtd->parent; - kref_put(&mtd->refcnt, mtd_device_release); + if (mtd != master) + kref_put(&mtd->refcnt, mtd_device_release); mtd = parent; }