From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f179.google.com (mail-qk1-f179.google.com [209.85.222.179]) (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 7FC1A3254A7 for ; Fri, 14 Nov 2025 14:44:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763131486; cv=none; b=UUdcc237gcxT2WUZgErZfowJOfgNuS8fAQYk1wzGrBmbHXr4X8NN/yGq3eVOeolH/u8Q1kXN1/xiDAHryIykNmSOk7aSbuu2phdElW2rc8ux+bk2kvGre9I6E05rrYluZmYEn6y5hHqqyqZMrMev/6z77Aax7ZiCEbofjdiI9W4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763131486; c=relaxed/simple; bh=ri3Ab/w8ylepNYDhS7++udAmqB7j+tQzODtC2zg91p8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YWt+m2RA4OcEnu+3xMgk5NV0JswaQkyVIv95QOFyRGeLI+UMLtw1+vBTlFC1vAk1bOZ3eu3noMh9Hi+aSu45k5L5o6zbViAX0leJL7VR31w2Envl+270j1q7+XHR5rhUy8lMongpsu94pQnoms1bU8MNpc5Eq/TJ2UfOwBlpHss= 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=E9B9K/ha; arc=none smtp.client-ip=209.85.222.179 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="E9B9K/ha" Received: by mail-qk1-f179.google.com with SMTP id af79cd13be357-88f2b29b651so194866085a.0 for ; Fri, 14 Nov 2025 06:44:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1763131483; x=1763736283; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=aWteGZHapM/ld2g8RPEQnKVKieUk3L8Us0utHpeCavw=; b=E9B9K/ha46D26PJezHpYj1Qq37r9xf9hnuH4vrf7MR6iHdRON8DCOZ7v2H+2GUZ9uL tw5riJIB4bPh0iRxPAzvc2gcHFxLV7fd4SOviyu92nRkFKOj3flpKGs0WbcJ1kcm9tRS hlYv9+xT0wBFbJK1vvyiHJxphi3NrgxbmxsODU4f3sy+R8AqTtF6uTadUVQeUPQtOaEK 16PZ/RcYDCyO7FMHIg6manGj28bv+d87em3RiygF8oOJIKT4oR6UqkNN+OPaYOdPXhPD m+PbKw/Q/uQ4iZK8mHcBC+kGcEk4VcwN2JebYBo1q+8Qh3cdHIntee2UloRw4FJpV1GG r0oA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763131483; x=1763736283; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=aWteGZHapM/ld2g8RPEQnKVKieUk3L8Us0utHpeCavw=; b=OlRjZdRTPCLeVBDYjlDYWl0ikohyo3+txvqQMjR/kFFgpe8vig0KDmKaQwFqSxKYWb Fiuoo+bwgU0mEBeX6/55eFDFpyPxMmLhc6TrraZCpvtQtCiB3z+7pPHaFWuTxYJTur2H 3Y9Ct4HU2zu9Q1aK58nS1LaeMZdZehfF4Y2+lKHdae5U1e++anGiT/0fc9ckHPZqLH5j Pp1W0bShaxB1upCBcU54dgAWa9vwY3BQbU8Riz7qlMblhKm5vLsmHQ+p+WM+HNz2UzFK B9Xj+DJG23ypRp4Ayg2GKxjsmnIAnIR3HpjICUSysuID+uH96kckmTyumuRJM20V1wGI YC6A== X-Gm-Message-State: AOJu0YxS2xpKgiN/DvaUVDco0NC1eoWEVQuQ9VjrKXVCA5GxqZVXt5Cr eOKueVFNDQySindF/SE2vtJnF0sDCP0JfFSuyBBDQyr8cZP11IDoPY/w X-Gm-Gg: ASbGncvkb3t3L1dE/+f3AeSD8Alq5C1oSCwhLOAQPs47Q/Nu5weQqlanK9V8u0kd1gO xTDJ7uq+xbX8CtKHFY6iDgfRyPetrofz0xv1URIjvofJXJ32soYmNEiVmGvjlJwKtcpOv6HfoIq UyimPvVfGy7k+wZ94M8PyfkavVyLbV9m8oI00QSKC4l7DHJ3swbCovQYRESBignzoAQoVXo8hlp vH3+Z3KUN2vAm+t1MOYlSS4CdI/0AgScWhVsHhj/2KOld3yXx/KrCZUhsgHJE65juo7eWoJJe8O 5PDNuL5xaVN7kpRdkIigOzeEocvo8JZLYnTFksSaHYX+HgW7KZP1Cn7FuIv8y9MPauv0OXtQGxz lHly7X+raZY8rqOqcM287mT49QgiYL/ikbBrxR+jcjXmNMUq2I8vP3bbBTgsjzQWUDG67Cyrq67 /Z7PpbK0Qm1oY3bJiZ0EX4K6/ZPvPb3+g= X-Google-Smtp-Source: AGHT+IFPjQlSqC/ss4lwRCrHnzgS910DC//wiBOCNwnW0xCnYqx8uCQ1I2xzaPFYMjeaq4Ndw+mQCQ== X-Received: by 2002:a05:620a:f15:b0:8b2:7726:c7cd with SMTP id af79cd13be357-8b2c31a622amr400786885a.49.1763131483265; Fri, 14 Nov 2025 06:44:43 -0800 (PST) Received: from rpthibeault-XPS-13-9305.. ([23.233.177.113]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8b2af048749sm344232285a.49.2025.11.14.06.44.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 06:44:42 -0800 (PST) From: Raphael Pinsonneault-Thibeault To: axboe@kernel.dk Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, jack@suse.cz, cascardo@igalia.com, linux-kernel-mentees@lists.linux.dev, skhan@linuxfoundation.org, syzbot+3ee481e21fd75e14c397@syzkaller.appspotmail.com, Raphael Pinsonneault-Thibeault Subject: [PATCH] loop: don't change loop device under exclusive opener in loop_set_status Date: Fri, 14 Nov 2025 09:42:05 -0500 Message-ID: <20251114144204.2402336-2-rpthibeault@gmail.com> X-Mailer: git-send-email 2.43.0 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 Signed-off-by: Raphael Pinsonneault-Thibeault --- ML thread for previous, misguided patch idea: https://lore.kernel.org/all/20251112185712.2031993-2-rpthibeault@gmail.com/t/ 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