From nobody Wed Jun 17 01:34:29 2026 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) (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 74578299937 for ; Wed, 29 Apr 2026 01:47:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.176 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777427245; cv=none; b=ascbG6QLHVw/wGkS5CZ/BTEthCgW2uMCDiDJ2QUA365Jjh44ttKnVChrIjx8SLyW8j2z6r1tDH/44FhhuU4iaP9HTo+o0QZQQpTghobjHkFXPogvr93LamfDQQsVHNz5ExN5sDQEkv+H8uaMsbKsjqH1M5FBRpBCgtc/QSY0lms= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777427245; c=relaxed/simple; bh=WqMv1YckYv/W8D1HJMKDMyO/iFhn+GXZHdYfC+bwTQA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=A/1s6BxYnhU1u8vIUuceBdl184kSjpDqlr5inPwNy+10dQ8bC9XURE/Gzk2xZ5mliTz9ArvGhA2yi9AfzvqeBs9t/WDMB3ON8wBdqhsK2njFl+Oey4PHYBdD0DghO9+TTLJVuFhabhTMQq5MtOSfamAfszDrarLpiIFxWc1brY0= 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=ZHmy7H+h; arc=none smtp.client-ip=209.85.210.176 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="ZHmy7H+h" Received: by mail-pf1-f176.google.com with SMTP id d2e1a72fcca58-82faf871346so7551977b3a.0 for ; Tue, 28 Apr 2026 18:47:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777427241; x=1778032041; 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=vQY4IGSDhnPDm3SZbmOaVwD/CLwLKCguemr0HTW+jZ8=; b=ZHmy7H+hQhl2GlGaGyksCcJZF4mFtKQriPFwIQZM7G4sg8hxYGULNwOoKjALh7t6rf IyIbwPzujwW3LmJveKhTbKDHkjScd4rG++y2cRM53oPPhe1uYHf6/OAcRo6ghI7lbWK0 RnOCTD9QM5loFrjJyERCKl2u5l64j4je34eVyqIEox3959fKZh+MXGQtONrAnnSiEVEm 3P4PJU0KWXZGQyq+iB3ufi4AGudcz6rLQUfXQt0n8x1HKLr1sU0Wc+xncD61Eswpbm0l zHlEiJS3GdJWnZNcVxKzroTF9OXLfpaYI8y5mIEoQhPQz1HrBQmdGH1PU5+N/Nv8mpn/ HxYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777427241; x=1778032041; 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=vQY4IGSDhnPDm3SZbmOaVwD/CLwLKCguemr0HTW+jZ8=; b=KSJAIrAmii5FZnsnNsBi81z+Lus2DF6rYKgqdVdtumInNyZmm3CqrvHFxwCXwDXWT2 7i62nZIZbvXw126udtObiInkPME0I9+JIbszIb7NzUi7eGylqiuQ9OIcHXoShNib+m8k P9FWZtwG81GBQ968uvyUaE3XGCzxATbvjSI9vZ0QPm/eMWGkMV4ZQ5e7HypoCORwmL6b EbbnJ/f1aw9816/5RqoW0omy6fbKg1lbmVtbC9QPc5nut7l9oIctNZVQjSxO/eEQOAQb xfuiHCoeiwLw9l6lSmASZtHldzcD2Ap2RTuvNoQ2d8NgC1sHyO4RxNwPUQFQyL07MZ05 2xVA== X-Forwarded-Encrypted: i=1; AFNElJ+DpAI5FgBh0oRozwS3fLCdysscB/KUk0RSBeV0+YDvX4PrmX/MifeuJ0cxgo09AspolYXimnMizlnL+h8=@vger.kernel.org X-Gm-Message-State: AOJu0YzAU2+MUfItmrffOt7F7T4uMTP6y1oK+vg+t0rvOGrrPykApWvX ouhttZYW1/4mKiuwg/IRtSwCH6KT7WeEaLHOY12z6+RGV9Sor6ggqSOY X-Gm-Gg: AeBDievILtjGiuZ376yBoYPDW6XuVz9GLvNvFx6moEcFhys6Vs6th+dClHFmp6Yt8nn K+1BZKVoXVXZrHT90fuSgiQKyDbB/wq+ePucOHLP8B2hQpX8YXa5ioON6NheGofO2JOGxRQpza0 2S/V5T2nv5Gkm6kw0WDLhJgqKRiZ7bz6mCB5rwKDGzhXadJmoTVx0GQ3RgwYAmxvs4PxMPxV3jM csluZRpgEZL7QL4fJVzSiRsxy7ouB4DhyFcQkTTS3Mwkho4wR3BH21M3ke4NePG7c+G/3cI/jpw 0UZb0rgd2EqhY2RISMDUbXwazBrv8RQdV07T/eCvGk85u98uJIl/qmGONeXOHY9IUGoRT/1FvFD g0+8KcX+gMC/KDXl1B/I2WxnOyYrJKGHm/5Ohnkd7A8CvMY+/p5tPljDiEq0XbEucu/tf5grPVO 8UgcoAmci8+lU/tX3S8JLDbG/XHC7kxP7iz+zKxsVngnMS/gZ9uc/5Hqts3G9SpufDYPhJwWFuA 3q/1J6MQ6c/PBP7gQ== X-Received: by 2002:a05:6a21:3290:b0:398:af16:f19f with SMTP id adf61e73a8af0-3a39c2742bemr6744689637.44.1777427241331; Tue, 28 Apr 2026 18:47:21 -0700 (PDT) Received: from deepanshu-kernel-hacker.. ([2405:201:682f:383f:4345:dc30:cb53:18e2]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-834ed6dd823sm331484b3a.38.2026.04.28.18.47.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 18:47:19 -0700 (PDT) From: Deepanshu Kartikey To: konishi.ryusuke@gmail.com, slava@dubeyko.com Cc: linux-nilfs@vger.kernel.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: [PATCH v2] nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers Date: Wed, 29 Apr 2026 07:17:11 +0530 Message-ID: <20260429014711.102110-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_SEGMEN= TS 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=3D62f0f99d2f2bb8e3bbd7 Fixes: 4f6b828837b4 ("nilfs2: fix lock order reversal in nilfs_clean_segmen= ts ioctl") Cc: stable@vger.kernel.org Tested-by: syzbot+62f0f99d2f2bb8e3bbd7@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/20260428040256.84403-1-kartikey406@gmail.= com/T/ [v1] Signed-off-by: Deepanshu Kartikey --- Changes in v2: - Reuse existing 'n' loop variable instead of introducing a new one (Slava Dubeyko) - Add dedicated out_free_segnums label so the validation-failure path falls through the existing cleanup ladder rather than duplicating kfree(kbufs[4]) inline (Slava Dubeyko) --- fs/nilfs2/ioctl.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c index e0a606643e87..41e47f558600 100644 --- a/fs/nilfs2/ioctl.c +++ b/fs/nilfs2/ioctl.c @@ -876,6 +876,20 @@ static int nilfs_ioctl_clean_segments(struct inode *in= ode, struct file *filp, } nilfs =3D inode->i_sb->s_fs_info; =20 + /* + * 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 (n =3D 0; n < nsegs; n++) { + if (((__u64 *)kbufs[4])[n] >=3D nilfs->ns_nsegments) { + ret =3D -EINVAL; + goto out_free_segnums; + } + } + for (n =3D 0; n < 4; n++) { ret =3D -EINVAL; if (argv[n].v_size !=3D argsz[n]) @@ -928,6 +942,7 @@ static int nilfs_ioctl_clean_segments(struct inode *ino= de, struct file *filp, out_free: while (--n >=3D 0) kvfree(kbufs[n]); +out_free_segnums: kfree(kbufs[4]); out: mnt_drop_write_file(filp); --=20 2.43.0