From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f70.google.com (mail-ot1-f70.google.com [209.85.210.70]) (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 2F5612EB10 for ; Mon, 27 Apr 2026 23:47:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777333657; cv=none; b=Vc6UU3fyCaDMkIRZavwkNvpePb7ZGR9FRBR/htRm9aolX5K/UHvjFOCzxenAszrysOUOe+5r/n7o9r1Y0XUB93ABU6BD/y4YULE9oMC97gamfRoHINaEDSgQmbbHFm/maWT7isNHOex4ArTzc85ems87rWAGKM62dtiRdhYwmOU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777333657; c=relaxed/simple; bh=wFqXzBFRjRrYp5Y0EJJKoQ5+geVGqfohS5qOFmJVquw=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=JV5cnCWD4N8znGa9PcURjhqEaMc8GaaNhoPtMTk81bZLqwz8YsE2HO0gnhxwjA3cQtGHS1DoA4O1nQqAtAwIXYddyDNWuIbOC9Z2YliGMQPAj02xtDXjVWLs1Y4OAPb1dqWebBMf/Z8MGq3x0udNpFKVrIVmZPLSOsGM2nCpa7M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.210.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-ot1-f70.google.com with SMTP id 46e09a7af769-7dbd60b7ecbso21419015a34.1 for ; Mon, 27 Apr 2026 16:47:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777333655; x=1777938455; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=N8Cgy5qfPjOmfB3/x9tGb3MgLqL6vVnFPS0Q4m2XvY8=; b=ESm6sZyg2kQF2XFjIucM18UDORTK11Xy6jMHXqTTtfDhfZ6m5EIxeslu1etP8nMNIh ySykR3w2E2Aw620lccuBT352qQNPplZ2623x7rOElexueTszBwLnGT/8Z4zal4R6QxVX 0J6PhdhZF5bflVXbR0aS+rbnvS7qvw5wISWn413uV1y63mXibKE8k5gtUHa1AsJdWHj4 ba9upves7TmuxQAlpqOUOtcb/kEbKVZdfZ1ujVAPgFKVOnoa70B+owGsuRRo1JEPGvZC DCyCtbZs/BpMrlYbp6/DxVeYkOgZFxCcizhnQQzZ6AFgZAAWFNc0yWvv5gdFitryRTt3 aYaQ== X-Gm-Message-State: AOJu0Yx/jXKrgpyFXw5goI1Xp4un4peK5A1Lr16Y7gXpWFbxUsykrn+P 86hhP+VA0EyFIEGxrsLBdM0WJz3OqzsthxPDPHB/A4Ae3PWLUrL7Kr+YD38a/QfE3WxA50iI3ay V5Sjonuaap3CdHBxgvVPCVPo/QGrSW/+A6crU0sZvjdhpYiaIVQsFJi5YbAw= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:808:b0:694:9861:ec5f with SMTP id 006d021491bc7-6965ca6bed1mr474233eaf.13.1777333655259; Mon, 27 Apr 2026 16:47:35 -0700 (PDT) Date: Mon, 27 Apr 2026 16:47:35 -0700 In-Reply-To: <69ef7af9.050a0220.1eaaa4.0002.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69eff597.050a0220.1eaaa4.0007.GAE@google.com> Subject: Forwarded: [PATCH] nilfs2: reject CLEAN_SEGMENTS ioctl with nsegs exceeding ns_nsegments From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] nilfs2: reject CLEAN_SEGMENTS ioctl with nsegs exceeding ns_nsegments Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master Syzbot reported a hung task in nilfs_transaction_begin() where multiple tasks performing chmod() on a nilfs2 mount blocked for over 143 seconds waiting to acquire ns_segctor_sem for read: INFO: task syz.0.17:5918 blocked for more than 143 seconds. Not tainted syzkaller #0 Call Trace: schedule+0x164/0x360 rwsem_down_read_slowpath+0x6d9/0x940 down_read+0x99/0x2e0 nilfs_transaction_begin+0x364/0x710 fs/nilfs2/segment.c:221 nilfs_setattr+0x124/0x2c0 fs/nilfs2/inode.c:921 notify_change+0xc1a/0xf40 chmod_common+0x273/0x4a0 do_fchmodat+0x12d/0x230 The writer holding ns_segctor_sem was a concurrent NILFS_IOCTL_CLEAN_SEGMENTS caller, stuck inside printk while emitting per-element warnings from nilfs_sufile_updatev(): __nilfs_msg+0x373/0x450 fs/nilfs2/super.c:78 nilfs_sufile_updatev+0x21c/0x6d0 fs/nilfs2/sufile.c:186 nilfs_sufile_freev fs/nilfs2/sufile.h:93 [inline] nilfs_free_segments fs/nilfs2/segment.c:1140 [inline] nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1261 [inline] nilfs_segctor_do_construct+0x1f55/0x76c0 nilfs_clean_segments+0x3bd/0xa50 nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:922 [inline] nilfs_ioctl+0x261f/0x2780 The root cause is that nilfs_ioctl_clean_segments() does not bound argv[4].v_nmembs (nsegs) against the actual number of segments on the filesystem. Userspace can therefore pass an arbitrarily large array of segment numbers, which is copied in via memdup_array_user() and then walked under both the sufile mi_sem and ns_segctor_sem (held for write by nilfs_clean_segments()). Each invalid entry produces a nilfs_warn() inside that critical section, and on a slow console the cumulative printk latency keeps ns_segctor_sem held long enough to trip the hung_task watchdog. Any concurrent operation needing ns_segctor_sem for read -- e.g. chmod() through nilfs_setattr() -- then stalls for the duration. While argv[0..3] are bounded by nsegs * ns_blocks_per_segment, nsegs itself is the root of that dependency chain and has no upper bound. There is no legitimate reason for a CLEAN_SEGMENTS request to reference more segments than exist on the filesystem. Reject such requests at the ioctl entry point so that the malformed input is refused before any FS-wide lock is acquired. Reported-by: syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=62f0f99d2f2bb8e3bbd7 Signed-off-by: Deepanshu Kartikey --- fs/nilfs2/ioctl.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c index e0a606643e87..a1688e940f7a 100644 --- a/fs/nilfs2/ioctl.c +++ b/fs/nilfs2/ioctl.c @@ -863,6 +863,9 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp, if (argv[4].v_size != argsz[4]) goto out; + nilfs = inode->i_sb->s_fs_info; + if (nsegs > nilfs->ns_nsegments) + goto out; /* * argv[4] points to segment numbers this ioctl cleans. We * use kmalloc() for its buffer because the memory used for the @@ -874,7 +877,6 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp, ret = PTR_ERR(kbufs[4]); goto out; } - nilfs = inode->i_sb->s_fs_info; for (n = 0; n < 4; n++) { ret = -EINVAL; -- 2.43.0