From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 14D5725485A for ; Wed, 17 Dec 2025 19:03:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.217.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765998199; cv=none; b=pCejEoEF53KPUin25VyaHKBC0tk1+faeUn28MIHLWX5bCzFA4pObtO6glh0NOSc2TjKM/udBuRS5FJLdUnek06Vv2xVTYowelora6qKv8hYL/qkYNLc4WKfGDU1so1L2We3Hf9ATO92OkDWpg7c3H/+MUomCW/pFCQR7OgVRnlM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765998199; c=relaxed/simple; bh=6IPbdt1L4AGkDZACFtU1zcBqo0Cbbff5QZYI76FNr+U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cvWz2n8cbLt0AXy1baPRiXC0NuTcHqzfCH0hnPvH8jUdjmfZqy6wh1Q5L4NmTMsktUkm+AQCqMtMK6cc2rT9OIzajzyBvKFKyXCNJcqHUBhayXx8GgpySYgml66wvc/IZxHCI5iDdM7VQWj/pSICCMPjMBmnG8JAvwM56hvlEvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=ZTLTw+qg; arc=none smtp.client-ip=209.85.217.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZTLTw+qg" Received: by mail-vs1-f52.google.com with SMTP id ada2fe7eead31-5eae7bb8018so579128137.2 for ; Wed, 17 Dec 2025 11:03:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1765998197; x=1766602997; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Oz8NDBC8rkRf0BKM+wNwYegVQjLipzJuVVp9JyHFbTo=; b=ZTLTw+qgAC7cXw8GoNUsjoxWRKZgCvpwuzi55V7GDQihbrehL0yTOHqaqm/dcF6vkQ tIVieKkO7dk8onaxrkIsL37gIWz4Z9At4WTaG4VOwp7EZjpZtc/+Sf3t9YrM4EoTlolu +aTJTsgRSRrQBHBgH5fD0KmSZdrXH+EDuGkIiz53qscm3NOLL7U8ewznmBRyiuSx9Psq PlYoxRiVyF+qGCYoJQwRpbR8BvXhTzhdAaVEMPVxRYOHonioNJKe1vl5H53zezYMNlBt g5OCi+MXSMhMUVd0k9bQPwdiz7QRujpeZ1e24bWj74VtE0hCzLuldO0DzLP8nIBJ1x9x JbNA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1765998197; x=1766602997; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=Oz8NDBC8rkRf0BKM+wNwYegVQjLipzJuVVp9JyHFbTo=; b=Mbr6CabRw5Fcx9BX6ZkTsvVb7CCCeZBVI42iGo9dxqt6XV525ydkm73zg1wns2LzMH uXiEGfcvdWkJocGuG7pubon11wvIUTySKeqJpMuzpA+PHAP1KSM3mFuTckbSj8j7q6Qp GOHdpdBK8kF5UMLo00x42BirgR4BeGLj3Q08qEsbtZxwSl49GpSa6RNE0fqv0bcXzSOw yxtiL8GQbXS57aMnzx8OEZ+MRd9svMxE6RnSwSN62xNFDyhhfb5O/T/IIRMwd8OEo7GK hYODnL0DGDp2TKBPsNmyWFMqRN8SdUE2FLq2nt3jcY3aD1fzN7J9nF2udzI+F7wSqS1e q0og== X-Forwarded-Encrypted: i=1; AJvYcCXIdWuVJIFfm1TF1PRj+AHxdKuG83ZH8KZra8C8OxcEttegSRPetzhN/fqg1RLS+50a5eiQDo6b3MQItQ==@vger.kernel.org X-Gm-Message-State: AOJu0Yz5MpXPtrExBFxjTSDiKCCruBKxYlyjO9gYezFo5ieDfq5XKHAJ cjl4EiXYVvheeINavrlyRJba8Ap4nIDhtUfppU7BbvzNTL5Tqsilrg9L X-Gm-Gg: AY/fxX5/8gDjo6//L4+6UJlp3uHJskHtvQAUYA8fosIOypNw2jrfH3Q2vSSqtWtPwLu 3BLLTzPBtD+QA39SJb2wmMcC32vJxN3b/f0IhHhuJ5XyLNAj9BYrG0myztwv5ffZNPNsxhXxxOJ oxMewiwibnRI1aTMlp5pmo3ry96Q8rWsTTW/TxeR5t39nPFIwyLCXKukxMo1xMGWgZ0csLGt8/J hb14liXVmJazEX2LSOT5bV1Zg1V7jXRA4yW7UNthJ6jgrG4CZhw5nPj1We/jRpvwNdVhkLJ3tBA B3Sh+45O9HF+AU3RUh1zHJ8gIRM/op5GhHwJhP1avoT1FZFazufHYkzu25hIMRvwapptti7GIw4 lV320U6Ui9TlZm5/a6VlrutFCNoJBhHuKkqmqU6zMhRXU+hg38jM4+sDy7Dih7HiTcPS3fDm4Cl Cv7Y78Scel29OEYfKEqsCh5IEoY4es63c= X-Google-Smtp-Source: AGHT+IEtFw7PJ5j7j9LgFaSmuKm/BvvOVGHX9z+Y+/Ht/9IPYaHhHPd/iE63FBwhRQqgHyc5KvxbvQ== X-Received: by 2002:a05:6102:4498:b0:5dd:a616:69fc with SMTP id ada2fe7eead31-5e827472567mr5852681137.9.1765998196849; Wed, 17 Dec 2025 11:03:16 -0800 (PST) Received: from rpthibeault-XPS-13-9305.. ([23.233.177.113]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88c61188285sm1365616d6.44.2025.12.17.11.03.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 11:03:16 -0800 (PST) From: Raphael Pinsonneault-Thibeault To: axboe@kernel.dk Cc: jack@suse.cz, syzbot+3ee481e21fd75e14c397@syzkaller.appspotmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, Raphael Pinsonneault-Thibeault , Yongpeng Yang Subject: [PATCH v2] loop: don't change loop device under exclusive opener in loop_set_status Date: Wed, 17 Dec 2025 14:00:40 -0500 Message-ID: <20251217190040.490204-2-rpthibeault@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2crvwmytxw5splvtauxdq6o3dt4rnnzuy22vcub45rjk354alr@6m66k3ucoics> References: <2crvwmytxw5splvtauxdq6o3dt4rnnzuy22vcub45rjk354alr@6m66k3ucoics> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit loop_set_status() is allowed to change the loop device while there are other openers of the device, even exclusive ones. In this case, it causes a KASAN: slab-out-of-bounds Read in ext4_search_dir(), since when looking for an entry in an inlined directory, e_value_offs is changed underneath the filesystem by loop_set_status(). Fix the problem by forbidding loop_set_status() from modifying the loop device while there are exclusive openers of the device. This is similar to the fix in loop_configure() by commit 33ec3e53e7b1 ("loop: Don't change loop device under exclusive opener") alongside commit ecbe6bc0003b ("block: use bd_prepare_to_claim directly in the loop driver"). Reported-by: syzbot+3ee481e21fd75e14c397@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3ee481e21fd75e14c397 Tested-by: syzbot+3ee481e21fd75e14c397@syzkaller.appspotmail.com Tested-by: Yongpeng Yang Signed-off-by: Raphael Pinsonneault-Thibeault Reviewed-by: Jan Kara --- v2: - added Tested-by and Reviewed-by tags for v1 drivers/block/loop.c | 41 ++++++++++++++++++++++++++++++----------- 1 file changed, 30 insertions(+), 11 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 053a086d547e..756ee682e767 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1222,13 +1222,24 @@ static int loop_clr_fd(struct loop_device *lo) } static int -loop_set_status(struct loop_device *lo, const struct loop_info64 *info) +loop_set_status(struct loop_device *lo, blk_mode_t mode, + struct block_device *bdev, const struct loop_info64 *info) { int err; bool partscan = false; bool size_changed = false; unsigned int memflags; + /* + * If we don't hold exclusive handle for the device, upgrade to it + * here to avoid changing device under exclusive owner. + */ + if (!(mode & BLK_OPEN_EXCL)) { + err = bd_prepare_to_claim(bdev, loop_set_status, NULL); + if (err) + goto out_reread_partitions; + } + err = mutex_lock_killable(&lo->lo_mutex); if (err) return err; @@ -1270,6 +1281,9 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info) } out_unlock: mutex_unlock(&lo->lo_mutex); + if (!(mode & BLK_OPEN_EXCL)) + bd_abort_claiming(bdev, loop_set_status); +out_reread_partitions: if (partscan) loop_reread_partitions(lo); @@ -1349,7 +1363,9 @@ loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info) } static int -loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg) +loop_set_status_old(struct loop_device *lo, blk_mode_t mode, + struct block_device *bdev, + const struct loop_info __user *arg) { struct loop_info info; struct loop_info64 info64; @@ -1357,17 +1373,19 @@ loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg) if (copy_from_user(&info, arg, sizeof (struct loop_info))) return -EFAULT; loop_info64_from_old(&info, &info64); - return loop_set_status(lo, &info64); + return loop_set_status(lo, mode, bdev, &info64); } static int -loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg) +loop_set_status64(struct loop_device *lo, blk_mode_t mode, + struct block_device *bdev, + const struct loop_info64 __user *arg) { struct loop_info64 info64; if (copy_from_user(&info64, arg, sizeof (struct loop_info64))) return -EFAULT; - return loop_set_status(lo, &info64); + return loop_set_status(lo, mode, bdev, &info64); } static int @@ -1546,14 +1564,14 @@ static int lo_ioctl(struct block_device *bdev, blk_mode_t mode, case LOOP_SET_STATUS: err = -EPERM; if ((mode & BLK_OPEN_WRITE) || capable(CAP_SYS_ADMIN)) - err = loop_set_status_old(lo, argp); + err = loop_set_status_old(lo, mode, bdev, argp); break; case LOOP_GET_STATUS: return loop_get_status_old(lo, argp); case LOOP_SET_STATUS64: err = -EPERM; if ((mode & BLK_OPEN_WRITE) || capable(CAP_SYS_ADMIN)) - err = loop_set_status64(lo, argp); + err = loop_set_status64(lo, mode, bdev, argp); break; case LOOP_GET_STATUS64: return loop_get_status64(lo, argp); @@ -1647,8 +1665,9 @@ loop_info64_to_compat(const struct loop_info64 *info64, } static int -loop_set_status_compat(struct loop_device *lo, - const struct compat_loop_info __user *arg) +loop_set_status_compat(struct loop_device *lo, blk_mode_t mode, + struct block_device *bdev, + const struct compat_loop_info __user *arg) { struct loop_info64 info64; int ret; @@ -1656,7 +1675,7 @@ loop_set_status_compat(struct loop_device *lo, ret = loop_info64_from_compat(arg, &info64); if (ret < 0) return ret; - return loop_set_status(lo, &info64); + return loop_set_status(lo, mode, bdev, &info64); } static int @@ -1682,7 +1701,7 @@ static int lo_compat_ioctl(struct block_device *bdev, blk_mode_t mode, switch(cmd) { case LOOP_SET_STATUS: - err = loop_set_status_compat(lo, + err = loop_set_status_compat(lo, mode, bdev, (const struct compat_loop_info __user *)arg); break; case LOOP_GET_STATUS: -- 2.43.0