From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0F7A3BCD05; Thu, 16 Jul 2026 14:10:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211032; cv=none; b=U9c0hbu4JHEvb827myrFY2KIoJYc8VJdI3QeO+YQn6p2rYuYf/mIpdGy6HRuH4uNFnevh9pCgGxhikc7KOWcRH1zw7HOq5dwroea4pbFQB/gA4ZLrNDJva9yiy2giGf08ZuzwZx03n2Y0sWSCR3E1RzVwIX+ZyxS30BKEpvW+io= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784211032; c=relaxed/simple; bh=SGQx2NoRwSpwBU9VuHGhvDpr2zAkPbCFGHoKckmUbW0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W9toUvnRQy45e8Lb2vBMLW90+DiEMMOwjXYscAaaszbDvQuW2FdfV4W0FUKbx9CNQjv9crId42w9kG5cwWWB0tcExHs5zapkGE/126ray2F+PPOgIyfAQRY0XzklCDGSQEUW3t+rEfI0heDEcrVAvR6ushoW33ltggYKN/00U4o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kex5M9wL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kex5M9wL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 243F71F000E9; Thu, 16 Jul 2026 14:10:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784211030; bh=q/bGCFrdB/bLrDXgM4BOhW/2P3txCYq8R7iyNIaVwLk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kex5M9wLa3VQTomqXTjE3l/sWIOiTuXxuLh+ZQOAsgce2J5SWoBG0BJpdhnGaUVea 1iweHg0Bfuv5RIQyPo/6IuR1pkt1iYsBhTqXjKOAzdJckD6OaMqRxxAnHCeOaZr8Jl 4Nsc8tLY1c6XKA+5PcrihY76vZ3Y/SZkSiQMwaMk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com, Deepanshu Kartikey , Ryusuke Konishi , Viacheslav Dubeyko Subject: [PATCH 6.18 271/480] nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers Date: Thu, 16 Jul 2026 15:30:18 +0200 Message-ID: <20260716133050.686872882@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Deepanshu Kartikey commit 0e7a690fe435f8d5ea3feb7c1d8d73ba7e8b8aa9 upstream. 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 user-supplied segment numbers are not validated before nilfs_clean_segments() begins doing work; 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 holding 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 nilfs_clean_segments() immediately after acquiring ns_segctor_sem via nilfs_transaction_lock(). Holding ns_segctor_sem serializes the check against nilfs_ioctl_resize(), which can modify ns_nsegments, so the validation uses a consistent value. Out-of-range segment numbers are rejected with -EINVAL before any segment-cleaning work begins, so the bad entries never reach the per-element diagnostic path inside nilfs_sufile_updatev(). Reported-by: syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=62f0f99d2f2bb8e3bbd7 Tested-by: syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Deepanshu Kartikey Fixes: 071cb4b81987 ("nilfs2: eliminate removal list of segments") Signed-off-by: Ryusuke Konishi Signed-off-by: Viacheslav Dubeyko Signed-off-by: Greg Kroah-Hartman --- fs/nilfs2/segment.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -2512,12 +2512,33 @@ int nilfs_clean_segments(struct super_bl struct nilfs_sc_info *sci = nilfs->ns_writer; struct nilfs_transaction_info ti; int err; + size_t i, nfreesegs = argv[4].v_nmembs; + __u64 *segnumv = kbufs[4]; if (unlikely(!sci)) return -EROFS; nilfs_transaction_lock(sb, &ti, 1); + /* + * Validate segment numbers under ns_segctor_sem (held for write + * by nilfs_transaction_lock above) so the check is serialized + * against nilfs_ioctl_resize(), which can modify ns_nsegments. + * Rejecting bad input here, before any segment-cleaning work + * begins, avoids the per-element diagnostic path inside + * nilfs_sufile_updatev() that would otherwise run under this + * same lock and stall concurrent readers. + */ + for (i = 0; i < nfreesegs; i++) { + if (segnumv[i] >= nilfs->ns_nsegments) { + nilfs_err(sb, + "Segment number %llu to be freed is out of range", + (unsigned long long)segnumv[i]); + err = -EINVAL; + goto bail_unlock; + } + } + err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat); if (unlikely(err)) goto out_unlock; @@ -2558,6 +2579,7 @@ int nilfs_clean_segments(struct super_bl sci->sc_freesegs = NULL; sci->sc_nfreesegs = 0; nilfs_mdt_clear_shadow_map(nilfs->ns_dat); + bail_unlock: nilfs_transaction_unlock(sb); return err; }