From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.2]) (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 BC4012475F7; Tue, 8 Sep 2026 05:30:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.2 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788845418; cv=none; b=HOoczxajDnPPTKzAPPu8RBfhI/rvOV2Hy8PS+x7ELrQwSdM/fDCc5/zwmsp4FwUEywlHq48PlBlm2aWO+Gjvkh0VWUNzNSdW2vOthLcCr7KD0qkD6a3rL3jktBaiTp0gOr++yBkXKTfkJfPNJAYvIa3QeVBnJV4gX+8lsU79fYk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788845418; c=relaxed/simple; bh=E6H2Y0ZwjLMFq5XqI2to9zCA8GhYxFW2g8SuFHNgAlM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XBWGQ9FxGdpbzTXBKPJSNVuClcz3MbG3Fv+8siQip9Yt5lUAznbq/Clyqlc8mEC5lXQTnGiXTLYdIq1+pz3PGv/sh88tK1o9h7h4Zr6PwQ9GCjdk/Z/K/KlWuo9zSLgrTvpP5iG8f6fNfxw2GL0Y+JHXGcHp8Mb2IloS6Qkw66Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=PJGaDQ9c; arc=none smtp.client-ip=220.197.31.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="PJGaDQ9c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Message-ID:Date:MIME-Version:Subject:To:From: Content-Type; bh=CLHtLxmz/iAPi/ljlw5y0pPU0Y71gzdqBytuxZnbHFQ=; b=PJGaDQ9c5DbKE0wEf9gxS8MFQbjKMP62y3NcKRy76meBWosXC85HamMDoQW142 sntu1I2ZtNfqiwb3Cf6G8b5HnrEpY+APgPYhvCmQ0pti8h2vhSTGHDgNiOgWThka Xkx5+s8/v7H8DCqjbVUDK7zcQ66cb95ddXa8/O2MsSagw= Received: from [IPV6:2409:8900:1e93:d74:46a:b98a:2b32:6a19] (unknown []) by gzga-smtp-mtada-g0-1 (Coremail) with SMTP id _____wA3YgJAnZ9qTDFdBQ--.20293S2; Tue, 08 Sep 2026 13:29:37 +0800 (CST) Message-ID: <9b5a4c9a-447c-4510-8d95-40c552dcbb73@163.com> Date: Tue, 8 Sep 2026 13:29:36 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] ntfs: fix volume flag update races To: Hongling Zeng , linkinjeon@kernel.org, hyc.lee@gmail.com Cc: ntfs@lists.linux.dev, linux-kernel@vger.kernel.org, zhongling0719@126.com, stable@vger.kernel.org References: <20260907070852.291323-1-zenghongling@kylinos.cn> <20260907070852.291323-2-zenghongling@kylinos.cn> Content-Language: en-US From: liubaolin In-Reply-To: <20260907070852.291323-2-zenghongling@kylinos.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wA3YgJAnZ9qTDFdBQ--.20293S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3WF4UZrWrAr4fCw1DGr1rZwb_yoW3JFyxpr sayF9rKa1qyrnrWws7tw4IgF4S9348Gr48Cry7Jw1av3sIyr1UXF18K3WrZFnYyr97Ar1x XFWUtrW5W3WUZFUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07U-Z2fUUUUU= X-CM-SenderInfo: xolxutxrol0iasrtmqqrwthudrp/xtbCwQH5xGqfnUFDTgAA3Z 在 2026/9/7 15:08, Hongling Zeng 写道: > ntfs_set_volume_flags() and ntfs_clear_volume_flags() both read > vol->vol_flags outside any lock to compute the new value before handing > it to ntfs_write_volume_flags(), which only takes ni->mrec_lock around > the actual write. The read-modify-write is therefore not atomic, and two > concurrent callers can lose an update: ntfs_sync_fs() may derive a > "clean" value from vol->vol_flags while a writer concurrently records an > error and sets VOLUME_IS_DIRTY; the locked write then silently > overwrites the freshly-set dirty bit. The on-disk volume looks clean > despite the recorded errors, so chkdsk will not run on the next mount > and corrupted metadata can persist. > > Fix by moving the read-modify-write inside the mrec_lock: pass the bits > to set and to clear separately, and combine them with the current flag > state under the lock inside ntfs_write_volume_flags(). The set/clear > helpers pass only the bits to modify, not the complete flag state. The > bit manipulation is done on CPU-endian values, and the result is > converted back to little-endian before storing it. The wrappers keep > their signatures so callers are unchanged. > > Cc: stable@vger.kernel.org > Signed-off-by: Hongling Zeng > --- > fs/ntfs/super.c | 63 +++++++++++++++++++++++++++++++++++-------------- > 1 file changed, 45 insertions(+), 18 deletions(-) > > diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c > index 60d43339c590..ce159ae8169a 100644 > --- a/fs/ntfs/super.c > +++ b/fs/ntfs/super.c > @@ -353,31 +353,45 @@ void ntfs_handle_error(struct super_block *sb) > } > > /* > - * ntfs_write_volume_flags - write new flags to the volume information flags > + * ntfs_write_volume_flags - apply flag changes to the volume information flags > * @vol: ntfs volume on which to modify the flags > - * @flags: new flags value for the volume information flags > + * @set_bits: bits to set in the volume information flags > + * @clear_bits: bits to clear in the volume information flags > * > * Internal function. You probably want to use ntfs_{set,clear}_volume_flags() > * instead (see below). > * > - * Replace the volume information flags on the volume @vol with the value > - * supplied in @flags. Note, this overwrites the volume information flags, so > - * make sure to combine the flags you want to modify with the old flags and use > - * the result when calling ntfs_write_volume_flags(). > + * Combine @set_bits and @clear_bits with the current in-memory flag state and > + * write the result back. The set/clear helpers pass only the bits to modify, > + * not the complete flag state. The read-modify-write happens under > + * ni->mrec_lock so that concurrent set/clear operations cannot lose updates. > + * All bit manipulation is done on CPU-endian values, and the result is > + * converted back to little-endian before storing it. > * > * Return 0 on success and -errno on error. > */ > -static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > +static int ntfs_write_volume_flags(struct ntfs_volume *vol, > + const __le16 set_bits, const __le16 clear_bits, > + const bool skip_if_errors) > { > struct ntfs_inode *ni = NTFS_I(vol->vol_ino); > struct volume_information *vi; > struct ntfs_attr_search_ctx *ctx; > + u16 flags; > int err; > > - ntfs_debug("Entering, old flags = 0x%x, new flags = 0x%x.", > - le16_to_cpu(vol->vol_flags), le16_to_cpu(flags)); > mutex_lock(&ni->mrec_lock); > - if (vol->vol_flags == flags) > + > + if (skip_if_errors && NVolErrors(vol)) > + goto done; > + > + flags = le16_to_cpu(vol->vol_flags); > + flags |= le16_to_cpu(set_bits) & le16_to_cpu(VOLUME_FLAGS_MASK); > + flags &= ~(le16_to_cpu(clear_bits) & le16_to_cpu(VOLUME_FLAGS_MASK)); > + ntfs_debug("Entering, old flags = 0x%x, new flags = 0x%x.", > + le16_to_cpu(vol->vol_flags), flags); > + > + if (le16_to_cpu(vol->vol_flags) == flags) > goto done; > > ctx = ntfs_attr_get_search_ctx(ni, NULL); > @@ -393,7 +407,7 @@ static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > > vi = (struct volume_information *)((u8 *)ctx->attr + > le16_to_cpu(ctx->attr->data.resident.value_offset)); > - vol->vol_flags = vi->flags = flags; > + vol->vol_flags = vi->flags = cpu_to_le16(flags); > mark_mft_record_dirty(ctx->ntfs_ino); > ntfs_attr_put_search_ctx(ctx); > done: > @@ -414,13 +428,14 @@ static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > * @flags: flags to set on the volume > * > * Set the bits in @flags in the volume information flags on the volume @vol. > + * The bits are combined with the current flag state under the lock in > + * ntfs_write_volume_flags(), so concurrent updates are not lost. > * > * Return 0 on success and -errno on error. > */ > int ntfs_set_volume_flags(struct ntfs_volume *vol, __le16 flags) > { > - flags &= VOLUME_FLAGS_MASK; > - return ntfs_write_volume_flags(vol, vol->vol_flags | flags); > + return ntfs_write_volume_flags(vol, flags, 0, false); > } Hi Hongling, Doesn't the caller-side check still leave a race here? Several paths in file.c and namei.c do: if (!(vol->vol_flags & VOLUME_IS_DIRTY)) ntfs_set_volume_flags(vol, VOLUME_IS_DIRTY); If the check sees the dirty bit set and sync_fs clears it before the metadata update, the caller skips setting it and the volume may be left clean. Since ntfs_write_volume_flags() already checks for an unchanged value under mrec_lock, should these callers invoke ntfs_set_volume_flags() unconditionally? Thanks, Baolin. > > /* > @@ -429,14 +444,27 @@ int ntfs_set_volume_flags(struct ntfs_volume *vol, __le16 flags) > * @flags: flags to clear on the volume > * > * Clear the bits in @flags in the volume information flags on the volume @vol. > + * The bits are combined with the current flag state under the lock in > + * ntfs_write_volume_flags(), so concurrent updates are not lost. > * > * Return 0 on success and -errno on error. > */ > int ntfs_clear_volume_flags(struct ntfs_volume *vol, __le16 flags) > { > - flags &= VOLUME_FLAGS_MASK; > - flags = vol->vol_flags & cpu_to_le16(~le16_to_cpu(flags)); > - return ntfs_write_volume_flags(vol, flags); > + return ntfs_write_volume_flags(vol, 0, flags, false); > +} > + > +/* > + * ntfs_clear_volume_dirty_if_no_errors - clear dirty bit if no errors exist > + * @vol: ntfs volume whose dirty bit should be cleared > + * > + * Check NVolErrors() and clear VOLUME_IS_DIRTY under the same mrec_lock so > + * ntfs_sync_fs() cannot clear the dirty bit after a concurrent error has been > + * recorded. > + */ > +static int ntfs_clear_volume_dirty_if_no_errors(struct ntfs_volume *vol) > +{ > + return ntfs_write_volume_flags(vol, 0, VOLUME_IS_DIRTY, true); > } > > int ntfs_write_volume_label(struct ntfs_volume *vol, char *label) > @@ -1862,8 +1890,7 @@ static int ntfs_sync_fs(struct super_block *sb, int wait) > return 0; > > /* If there are some dirty buffers in the bdev inode */ > - if (!NVolErrors(vol) && > - ntfs_clear_volume_flags(vol, VOLUME_IS_DIRTY)) { > + if (ntfs_clear_volume_dirty_if_no_errors(vol)) { > ntfs_warning(sb, "Failed to clear dirty bit in volume information flags. Run chkdsk."); > err = -EIO; > }