From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f70.google.com (mail-oo1-f70.google.com [209.85.161.70]) (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 015175464D for ; Tue, 28 Apr 2026 00:31:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777336313; cv=none; b=svJ+TPK8KD1ynt8WZlSFpACStgbIGBrVLqksrI5nWZ+gAlyea4WjcVvQQ1B6W5x+XWHZlODpt4WShQhPQvF/BPHYxIT1Q1GyhaWWZLYYglWkhmm4En/9slm/W4abjLyIjchYzV2rEgm0MnpaTWuaIsP+D7kagrK9TeExqk8drmo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777336313; c=relaxed/simple; bh=6Nqw657KwcXidM3kn6UAPQx/fZveEvkDgVzJaQpgjMw=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=AehFMh5BzivQ+Hvez4TLrbYxzLUQ1fw9cxhIr1wQ+zCwwjxkz1Sn3M8SeUUSzplOYrHf1BDj0mGap48iw5DDtqbVyLLUnlRxZcdxIN0hxKnehwY8bnX7s4OR9C6VYolZbMiFH4Gg8FM/ZmbaRzdKH2Em/WNEA2t5C5RWz5WCKoA= 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=209.85.161.70 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-oo1-f70.google.com with SMTP id 006d021491bc7-6947f168159so16746689eaf.2 for ; Mon, 27 Apr 2026 17:31:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777336311; x=1777941111; 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=hKuF7mzCJbOlJzLbP7Sp58jceWjxdZP0GtBM52rY9Yo=; b=MC+l8Z09zltHGZ/sGBigEzzwxRtGQdOXhEFYuFPeXTrQAh5vRD7aeWfQmN41xamlBs /gOhLN/kZVzQUafEesXxor/4hSAHev+Q4LRZ3YA9YbxHsBPMPOc53H7ooNufxvX1d8dh ULyatC+HfzuVfYkJZvkhOXVSGTL7TY2l0Ym7zLQWq7mvEC9Iro+nAiqqZJVwvYg6jH2F Ee13Mb++QGexkrdwRoV03C8Pec63LygwT9JjmEtAbtN5cuSgYZmubmLm2OwqD3zVOjSp 4ZTmjH5dxwu/pCouxhm5uJpjo31/7d80/YYkoVIxU5tb+o3Okizdu6bQ9Brv+Ojl5GEc jQfw== X-Gm-Message-State: AOJu0YwBrqSv/xBTXc97mFRlfwK1yyKyK/awrbGbAoRHUxs0lwKlj/pt OiLcogCyWe9JTFrKuxbdDepB32+ZNtzM+2HgBmdDmgFtcFXxMw5C6oBHgxdBv6tyfaMSAbYEewb +D2vFvWY+PDHiSRnqE1DVoknh9WsbNMO2rEisa4U+1l9HXYPwl8BBQAlG4uI= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:4deb:b0:696:17a7:140c with SMTP id 006d021491bc7-6965ca83431mr430274eaf.23.1777336310978; Mon, 27 Apr 2026 17:31:50 -0700 (PDT) Date: Mon, 27 Apr 2026 17:31:50 -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: <69effff6.050a0220.18b4f.0009.GAE@google.com> Subject: Forwarded: [PATCH] nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers 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 out-of-range segment numbers 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. 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 validate the user-supplied segment numbers in kbufs[4] before calling nilfs_clean_segments(), which acquires ns_segctor_sem for write. The range check on each segnum is performed deep inside the call chain by nilfs_sufile_updatev(), which emits a nilfs_warn() per invalid entry while still under the segctor lock and the sufile mi_sem. Under load (repeated invocations across multiple mounts saturating the global printk path), the cumulative printk latency keeps ns_segctor_sem held long enough to trip the hung_task watchdog, blocking concurrent operations such as chmod() that need ns_segctor_sem for read. Fix by validating the contents of kbufs[4] in the ioctl entry path, before any FS-wide lock is acquired. Out-of-range segment numbers are rejected with -EINVAL synchronously, with no work performed under ns_segctor_sem. Reported-by: syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=62f0f99d2f2bb8e3bbd7 Signed-off-by: Deepanshu Kartikey --- fs/nilfs2/ioctl.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c index e0a606643e87..38822dce1839 100644 --- a/fs/nilfs2/ioctl.c +++ b/fs/nilfs2/ioctl.c @@ -846,6 +846,7 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp, struct the_nilfs *nilfs; size_t len, nsegs; int n, ret; + size_t i; if (!capable(CAP_SYS_ADMIN)) return -EPERM; @@ -876,6 +877,21 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp, } nilfs = inode->i_sb->s_fs_info; + /* + * Validate segment numbers against the filesystem's segment count + * before entering nilfs_clean_segments(), which acquires + * ns_segctor_sem for write. Catching invalid segnums here avoids + * holding that lock while emitting per-element diagnostics under + * the segment constructor. + */ + for (i = 0; i < nsegs; i++) { + if (((__u64 *)kbufs[4])[i] >= nilfs->ns_nsegments) { + ret = -EINVAL; + kfree(kbufs[4]); + goto out; + } + } + for (n = 0; n < 4; n++) { ret = -EINVAL; if (argv[n].v_size != argsz[n]) -- 2.43.0