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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-74af5571b7asm10130516b3a.85.2025.06.30.14.22.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Jun 2025 14:22:48 -0700 (PDT) Message-ID: <3cfa190e-fa9b-45b7-a6a3-8d067f2cc197@suse.com> Date: Tue, 1 Jul 2025 06:52:44 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] btrfs: qgroup: fix race between quota disable and quota rescan ioctl To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <19f775a9f256c4a5146cc97b7f521464429c81bc.1751288689.git.fdmanana@suse.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <19f775a9f256c4a5146cc97b7f521464429c81bc.1751288689.git.fdmanana@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/6/30 22:37, fdmanana@kernel.org 写道: > From: Filipe Manana > > There's a race between a task disabling quotas and another running the > rescan ioctl that can result in a use-after-free of qgroup records from > the fs_info->qgroup_tree rbtree. > > This happens as follows: > > 1) Task A enters btrfs_ioctl_quota_rescan() -> btrfs_qgroup_rescan(); > > 2) Task B enters btrfs_quota_disable() and calls > btrfs_qgroup_wait_for_completion(), which does nothing because at that > point fs_info->qgroup_rescan_running is false (it wasn't set yet by > task A); > > 3) Task B calls btrfs_free_qgroup_config() which starts freeing qgroups > from fs_info->qgroup_tree without taking the lock fs_info->qgroup_lock; > > 4) Task A enters qgroup_rescan_zero_tracking() which starts iterating > the fs_info->qgroup_tree tree while holding fs_info->qgroup_lock, > but task B is freeing qgroup records from that tree without holding > the lock, resulting in a use-after-free. > > Fix this by taking fs_info->qgroup_lock at btrfs_free_qgroup_config(). > Also at btrfs_qgroup_rescan() don't start the rescan worker if quotas > were already disabled. > > Reported-by: cen zhang > Link: https://lore.kernel.org/linux-btrfs/CAFRLqsV+cMDETFuzqdKSHk_FDm6tneea45krsHqPD6B3FetLpQ@mail.gmail.com/ > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > fs/btrfs/qgroup.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index b83d9534adae..8fa874ef80b3 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -636,22 +636,30 @@ bool btrfs_check_quota_leak(const struct btrfs_fs_info *fs_info) > > /* > * This is called from close_ctree() or open_ctree() or btrfs_quota_disable(), > - * first two are in single-threaded paths.And for the third one, we have set > - * quota_root to be null with qgroup_lock held before, so it is safe to clean > - * up the in-memory structures without qgroup_lock held. > + * first two are in single-threaded paths. > */ > void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info) > { > struct rb_node *n; > struct btrfs_qgroup *qgroup; > > + /* > + * btrfs_quota_disable() can be called concurrently with > + * btrfs_qgroup_rescan() -> qgroup_rescan_zero_tracking(), so take the > + * lock. > + */ > + spin_lock(&fs_info->qgroup_lock); > while ((n = rb_first(&fs_info->qgroup_tree))) { > qgroup = rb_entry(n, struct btrfs_qgroup, node); > rb_erase(n, &fs_info->qgroup_tree); > __del_qgroup_rb(qgroup); > + spin_unlock(&fs_info->qgroup_lock); > btrfs_sysfs_del_one_qgroup(fs_info, qgroup); > kfree(qgroup); > + spin_lock(&fs_info->qgroup_lock); > } > + spin_unlock(&fs_info->qgroup_lock); > + > /* > * We call btrfs_free_qgroup_config() when unmounting > * filesystem and disabling quota, so we set qgroup_ulist > @@ -4036,12 +4044,16 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info) > qgroup_rescan_zero_tracking(fs_info); > > mutex_lock(&fs_info->qgroup_rescan_lock); > - fs_info->qgroup_rescan_running = true; > - btrfs_queue_work(fs_info->qgroup_rescan_workers, > - &fs_info->qgroup_rescan_work); > + if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) { > + fs_info->qgroup_rescan_running = true; > + btrfs_queue_work(fs_info->qgroup_rescan_workers, > + &fs_info->qgroup_rescan_work); > + } else { > + ret = -ENOTCONN; > + } > mutex_unlock(&fs_info->qgroup_rescan_lock); > > - return 0; > + return ret; > } > > int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,