一、漏洞信息
漏洞编号:CVE-2021-46987
漏洞归属组件:kernel
漏洞归属的版本:4.19.140,4.19.194,4.19.90,5.10.0,6.1.0,6.1.14,6.1.19,6.1.5,6.1.6,6.1.8,6.4.0
CVSS V2.0分值:
BaseScore:0.0 Low
Vector:CVSS:2.0/
漏洞简述:
In the Linux kernel, the following vulnerability has been resolved:btrfs: fix deadlock when cloning inline extents and using qgroupsThere are a few exceptional cases where cloning an inline extent needs tocopy the inline extent data into a page of the destination inode.When this happens, we end up starting a transaction while having a dirtypage for the destination inode and while having the range locked in thedestination s inode iotree too. Because when reserving metadata spacefor a transaction we may need to flush existing delalloc in case there isnot enough free space, we have a mechanism in place to prevent a deadlock,which was introduced in commit 3d45f221ce627d ( btrfs: fix deadlock whencloning inline extent and low on free metadata space ).However when using qgroups, a transaction also reserves metadata qgroupspace, which can also result in flushing delalloc in case there is notenough available space at the moment. When this happens we deadlock, sinceflushing delalloc requires locking the file range in the inode s iotreeand the range was already locked at the very beginning of the cloneoperation, before attempting to start the transaction.When this issue happens, stack traces like the following are reported: [72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142) [72747.556271] Call Trace: [72747.556273] __schedule+0x296/0x760 [72747.556277] schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extent_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extent_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747.556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] process_one_work+0x1aa/0x340 [72747.556426] worker_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30 [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Call Trace: [72747.566964] __schedule+0x296/0x760 [72747.566968] ? finish_wait+0x80/0x80 [72747.566970] schedule+0x3c/0xa0 [72747.566995] wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051] ? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extent_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extent_writepages+0x44/0xa0 [btrfs] [72747.567137] ? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] process_one_work+0x1aa/0x340 [72747.567202] worker_thread+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211] ? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30 [72747.569686] task:fsstress state:D stack: ---truncated---
漏洞公开时间:2024-02-28 17:15:37
漏洞创建时间:2024-02-29 00:16:12
漏洞详情参考链接:
https://nvd.nist.gov/vuln/detail/CVE-2021-46987
参考来源 | 参考链接 | 来源链接 |
---|---|---|
416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/96157707c0420e3d3edfe046f1cc797fee117ade | |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/d5347827d0b4b2250cbce6eccaa1c81dc78d8651 | |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/f9baa501b4fd6962257853d46ddffbc21f27e344 | |
redhat_bugzilla | https://lore.kernel.org/linux-cve-announce/2024022825-CVE-2021-46987-f73f@gregkh/T/#u | https://bugzilla.redhat.com/show_bug.cgi?id=2266752 |
漏洞分析指导链接:
https://gitee.com/openeuler/cve-manager/blob/master/cve-vulner-manager/doc/md/manual.md
漏洞数据来源:
openBrain开源漏洞感知系统
漏洞补丁信息:
无
二、漏洞分析结构反馈
影响性分析说明:
In the Linux kernel, the following vulnerability has been resolved:btrfs: fix deadlock when cloning inline extents and using qgroupsThere are a few exceptional cases where cloning an inline extent needs tocopy the inline extent data into a page of the destination inode.When this happens, we end up starting a transaction while having a dirtypage for the destination inode and while having the range locked in thedestination s inode iotree too. Because when reserving metadata spacefor a transaction we may need to flush existing delalloc in case there isnot enough free space, we have a mechanism in place to prevent a deadlock,which was introduced in commit 3d45f221ce627d ( btrfs: fix deadlock whencloning inline extent and low on free metadata space ).However when using qgroups, a transaction also reserves metadata qgroupspace, which can also result in flushing delalloc in case there is notenough available space at the moment. When this happens we deadlock, sinceflushing delalloc requires locking the file range in the inode s iotreeand the range was already locked at the very beginning of the cloneoperation, before attempting to start the transaction.When this issue happens, stack traces like the following are reported: [72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000 [72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142) [72747.556271] Call Trace: [72747.556273] __schedule+0x296/0x760 [72747.556277] schedule+0x3c/0xa0 [72747.556279] io_schedule+0x12/0x40 [72747.556284] __lock_page+0x13c/0x280 [72747.556287] ? generic_file_readonly_mmap+0x70/0x70 [72747.556325] extent_write_cache_pages+0x22a/0x440 [btrfs] [72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160 [72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs] [72747.556362] ? update_group_capacity+0x25/0x210 [72747.556366] ? cpumask_next_and+0x1a/0x20 [72747.556391] extent_writepages+0x44/0xa0 [btrfs] [72747.556394] do_writepages+0x41/0xd0 [72747.556398] __writeback_single_inode+0x39/0x2a0 [72747.556403] writeback_sb_inodes+0x1ea/0x440 [72747.556407] __writeback_inodes_wb+0x5f/0xc0 [72747.556410] wb_writeback+0x235/0x2b0 [72747.556414] ? get_nr_inodes+0x35/0x50 [72747.556417] wb_workfn+0x354/0x490 [72747.556420] ? newidle_balance+0x2c5/0x3e0 [72747.556424] process_one_work+0x1aa/0x340 [72747.556426] worker_thread+0x30/0x390 [72747.556429] ? create_worker+0x1a0/0x1a0 [72747.556432] kthread+0x116/0x130 [72747.556435] ? kthread_park+0x80/0x80 [72747.556438] ret_from_fork+0x1f/0x30 [72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs] [72747.566961] Call Trace: [72747.566964] __schedule+0x296/0x760 [72747.566968] ? finish_wait+0x80/0x80 [72747.566970] schedule+0x3c/0xa0 [72747.566995] wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs] [72747.566999] ? finish_wait+0x80/0x80 [72747.567024] lock_extent_bits+0x37/0x90 [btrfs] [72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs] [72747.567051] ? find_get_pages_range_tag+0x2cd/0x380 [72747.567076] __extent_writepage+0x203/0x320 [btrfs] [72747.567102] extent_write_cache_pages+0x2bb/0x440 [btrfs] [72747.567106] ? update_load_avg+0x7e/0x5f0 [72747.567109] ? enqueue_entity+0xf4/0x6f0 [72747.567134] extent_writepages+0x44/0xa0 [btrfs] [72747.567137] ? enqueue_task_fair+0x93/0x6f0 [72747.567140] do_writepages+0x41/0xd0 [72747.567144] __filemap_fdatawrite_range+0xc7/0x100 [72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs] [72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs] [72747.567200] process_one_work+0x1aa/0x340 [72747.567202] worker_thread+0x30/0x390 [72747.567205] ? create_worker+0x1a0/0x1a0 [72747.567208] kthread+0x116/0x130 [72747.567211] ? kthread_park+0x80/0x80 [72747.567214] ret_from_fork+0x1f/0x30 [72747.569686] task:fsstress state:D stack: ---truncated---
openEuler评分:
5.5
Vector:CVSS:2.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
受影响版本排查(受影响/不受影响):
1.openEuler-22.03-LTS(5.10.0):受影响
2.openEuler-22.03-LTS-SP1(5.10.0):受影响
3.openEuler-22.03-LTS-SP2(5.10.0):受影响
4.openEuler-22.03-LTS-SP3:受影响
5.openEuler-22.03-LTS-Next(5.10.0):受影响
6.openEuler-20.03-LTS-SP1(4.19.90):不受影响
7.openEuler-20.03-LTS-SP4:不受影响
8.master(6.1.0):不受影响
9.openEuler-24.03-LTS:不受影响
修复是否涉及abi变化(是/否):
1.openEuler-20.03-LTS-SP1(4.19.90):否
2.openEuler-20.03-LTS-SP4:否
3.openEuler-22.03-LTS(5.10.0):否
4.openEuler-22.03-LTS-SP1(5.10.0):否
5.openEuler-22.03-LTS-SP2(5.10.0):否
6.openEuler-22.03-LTS-SP3:否
7.master(6.1.0):否
8.openEuler-22.03-LTS-Next(5.10.0):否
9.openEuler-24.03-LTS:否
三、漏洞修复
安全公告链接:https://www.openeuler.org/zh/security/safety-bulletin/detail/?id=openEuler-SA-2024-1301
此处可能存在不合适展示的内容,页面不予展示。您可通过相关编辑功能自查并修改。
如您确认内容无涉及 不当用语 / 纯广告导流 / 暴力 / 低俗色情 / 侵权 / 盗版 / 虚假 / 无价值内容或违法国家有关法律法规的内容,可点击提交进行申诉,我们将尽快为您处理。
@YangYingliang ,@成坚 (CHENG Jian) ,@jiaoff ,@AlexGuo ,@hanjun-guo ,@woqidaideshi ,@Jackie Liu ,@Zhang Yi ,@colyli ,@ThunderTown ,@htforge ,@Chiqijun ,@冷嘲啊 ,@zhujianwei001 ,@kylin-mayukun ,@wangxiongfeng ,@Kefeng ,@SuperSix173 ,@WangShaoBo ,@Zheng Zucheng
issue处理注意事项:
1. 当前issue受影响的分支提交pr时, 须在pr描述中填写当前issue编号进行关联, 否则无法关闭当前issue;
2. 模板内容需要填写完整, 无论是受影响或者不受影响都需要填写完整内容,未引入的分支不需要填写, 否则无法关闭当前issue;
3. 以下为模板中需要填写完整的内容, 请复制到评论区回复, 注: 内容的标题名称(影响性分析说明, openEuler评分, 受影响版本排查(受影响/不受影响), 修复是否涉及abi变化(是/否))不能省略,省略后cve-manager将无法正常解析填写内容.
影响性分析说明:
openEuler评分: (评分和向量)
受影响版本排查(受影响/不受影响):
1.master(6.1.0):
2.openEuler-20.03-LTS-SP1(4.19.90):
3.openEuler-20.03-LTS-SP4(4.19.90):
4.openEuler-22.03-LTS(5.10.0):
5.openEuler-22.03-LTS-Next(5.10.0):
6.openEuler-22.03-LTS-SP1(5.10.0):
7.openEuler-22.03-LTS-SP2(5.10.0):
8.openEuler-22.03-LTS-SP3(5.10.0):
修复是否涉及abi变化(是/否):
1.master(6.1.0):
2.openEuler-20.03-LTS-SP1(4.19.90):
3.openEuler-20.03-LTS-SP4(4.19.90):
4.openEuler-22.03-LTS(5.10.0):
5.openEuler-22.03-LTS-Next(5.10.0):
6.openEuler-22.03-LTS-SP1(5.10.0):
7.openEuler-22.03-LTS-SP2(5.10.0):
8.openEuler-22.03-LTS-SP3(5.10.0):
issue处理具体操作请参考:
https://gitee.com/openeuler/cve-manager/blob/master/cve-vulner-manager/doc/md/manual.md
pr关联issue具体操作请参考:
https://gitee.com/help/articles/4142
参考网址 | 关联pr | 状态 | 补丁链接 |
---|---|---|---|
https://nvd.nist.gov/vuln/detail/CVE-2021-46987 | None | None |
https://git.kernel.org/stable/c/d5347827d0b4b2250cbce6eccaa1c81dc78d8651 https://git.kernel.org/stable/c/f9baa501b4fd6962257853d46ddffbc21f27e344 https://git.kernel.org/stable/c/96157707c0420e3d3edfe046f1cc797fee117ade |
https://ubuntu.com/security/CVE-2021-46987 | None | None | https://discourse.ubuntu.com/c/ubuntu-pro |
https://www.opencve.io/cve/CVE-2021-46987 | None | None |
https://git.kernel.org/stable/c/d5347827d0b4b2250cbce6eccaa1c81dc78d8651 https://git.kernel.org/stable/c/f9baa501b4fd6962257853d46ddffbc21f27e344 https://git.kernel.org/stable/c/96157707c0420e3d3edfe046f1cc797fee117ade |
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2021-46987 | |||
https://security-tracker.debian.org/tracker/CVE-2021-46987 | None | None | https://git.kernel.org/linus/f9baa501b4fd6962257853d46ddffbc21f27e344 |
说明:补丁链接仅供初步排查参考,实际可用性请人工再次确认,补丁下载验证可使用CVE补丁工具。
若补丁不准确,烦请在此issue下评论 '/report-patch 参考网址 补丁链接1,补丁链接2' 反馈正确信息,便于我们不断优化工具,不胜感激。
如 /report-patch https://security-tracker.debian.org/tracker/CVE-2021-3997 https://github.com/systemd/systemd/commit/5b1cf7a9be37e20133c0208005274ce4a5b5c6a1
@ci-robot 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
@zhangjialin 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
@zhangjialin 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
@openeuler-sync-bot 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3,openEuler-24.03-LTS 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
@openeuler-sync-bot 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3,openEuler-24.03-LTS 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
@openeuler-sync-bot 请确认分支: master,openEuler-20.03-LTS-SP1,openEuler-20.03-LTS-SP4,openEuler-22.03-LTS,openEuler-22.03-LTS-Next,openEuler-22.03-LTS-SP1,openEuler-22.03-LTS-SP2,openEuler-22.03-LTS-SP3,openEuler-24.03-LTS 受影响/不受影响.
请确认分支信息是否填写完整,否则将无法关闭当前issue.
CVE-2021-46987
影响性分析说明:
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix deadlock when cloning inline extents and using qgroups
There are a few exceptional cases where cloning an inline extent needs to
copy the inline extent data into a page of the destination inode.
When this happens, we end up starting a transaction while having a dirty
page for the destination inode and while having the range locked in the
destination's inode iotree too. Because when reserving metadata space
for a transaction we may need to flush existing delalloc in case there is
not enough free space, we have a mechanism in place to prevent a deadlock,
which was introduced in commit 3d45f221ce627d ("btrfs: fix deadlock when
cloning inline extent and low on free metadata space").
However when using qgroups, a transaction also reserves metadata qgroup
space, which can also result in flushing delalloc in case there is not
enough available space at the moment. When this happens we deadlock, since
flushing delalloc requires locking the file range in the inode's iotree
and the range was already locked at the very beginning of the clone
operation, before attempting to start the transaction.
When this issue happens, stack traces like the following are reported:
[72747.556262] task:kworker/u81:9 state:D stack: 0 pid: 225 ppid: 2 flags:0x00004000
[72747.556268] Workqueue: writeback wb_workfn (flush-btrfs-1142)
[72747.556271] Call Trace:
[72747.556273] __schedule+0x296/0x760
[72747.556277] schedule+0x3c/0xa0
[72747.556279] io_schedule+0x12/0x40
[72747.556284] __lock_page+0x13c/0x280
[72747.556287] ? generic_file_readonly_mmap+0x70/0x70
[72747.556325] extent_write_cache_pages+0x22a/0x440 [btrfs]
[72747.556331] ? __set_page_dirty_nobuffers+0xe7/0x160
[72747.556358] ? set_extent_buffer_dirty+0x5e/0x80 [btrfs]
[72747.556362] ? update_group_capacity+0x25/0x210
[72747.556366] ? cpumask_next_and+0x1a/0x20
[72747.556391] extent_writepages+0x44/0xa0 [btrfs]
[72747.556394] do_writepages+0x41/0xd0
[72747.556398] __writeback_single_inode+0x39/0x2a0
[72747.556403] writeback_sb_inodes+0x1ea/0x440
[72747.556407] __writeback_inodes_wb+0x5f/0xc0
[72747.556410] wb_writeback+0x235/0x2b0
[72747.556414] ? get_nr_inodes+0x35/0x50
[72747.556417] wb_workfn+0x354/0x490
[72747.556420] ? newidle_balance+0x2c5/0x3e0
[72747.556424] process_one_work+0x1aa/0x340
[72747.556426] worker_thread+0x30/0x390
[72747.556429] ? create_worker+0x1a0/0x1a0
[72747.556432] kthread+0x116/0x130
[72747.556435] ? kthread_park+0x80/0x80
[72747.556438] ret_from_fork+0x1f/0x30
[72747.566958] Workqueue: btrfs-flush_delalloc btrfs_work_helper [btrfs]
[72747.566961] Call Trace:
[72747.566964] __schedule+0x296/0x760
[72747.566968] ? finish_wait+0x80/0x80
[72747.566970] schedule+0x3c/0xa0
[72747.566995] wait_extent_bit.constprop.68+0x13b/0x1c0 [btrfs]
[72747.566999] ? finish_wait+0x80/0x80
[72747.567024] lock_extent_bits+0x37/0x90 [btrfs]
[72747.567047] btrfs_invalidatepage+0x299/0x2c0 [btrfs]
[72747.567051] ? find_get_pages_range_tag+0x2cd/0x380
[72747.567076] __extent_writepage+0x203/0x320 [btrfs]
[72747.567102] extent_write_cache_pages+0x2bb/0x440 [btrfs]
[72747.567106] ? update_load_avg+0x7e/0x5f0
[72747.567109] ? enqueue_entity+0xf4/0x6f0
[72747.567134] extent_writepages+0x44/0xa0 [btrfs]
[72747.567137] ? enqueue_task_fair+0x93/0x6f0
[72747.567140] do_writepages+0x41/0xd0
[72747.567144] __filemap_fdatawrite_range+0xc7/0x100
[72747.567167] btrfs_run_delalloc_work+0x17/0x40 [btrfs]
[72747.567195] btrfs_work_helper+0xc2/0x300 [btrfs]
[72747.567200] process_one_work+0x1aa/0x340
[72747.567202] worker_thread+0x30/0x390
[72747.567205] ? create_worker+0x1a0/0x1a0
[72747.567208] kthread+0x116/0x130
[72747.567211] ? kthread_park+0x80/0x80
[72747.567214] ret_from_fork+0x1f/0x30
[72747.569686] task:fsstress state:D stack:
---truncated---
openEuler评分:(评分和向量)
5.5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
受影响版本排查(受影响/不受影响):
1.openEuler-20.03-LTS-SP1(4.19.90):不受影响
2.openEuler-20.03-LTS-SP4:不受影响
3.openEuler-22.03-LTS:受影响
4.openEuler-22.03-LTS-SP1:受影响
5.openEuler-22.03-LTS-SP2:受影响
6.openEuler-22.03-LTS-SP3:受影响
7.master(6.1.0):不受影响
8.openEuler-22.03-LTS-Next:受影响
9.openEuler-24.03-LTS:不受影响
修复是否涉及abi变化(是/否):
1.openEuler-20.03-LTS-SP1(4.19.90):否
2.openEuler-20.03-LTS-SP4:否
3.openEuler-22.03-LTS:否
4.openEuler-22.03-LTS-SP1:否
5.openEuler-22.03-LTS-SP2:否
6.openEuler-22.03-LTS-SP3:否
7.master(6.1.0):否
8.openEuler-22.03-LTS-Next:否
9.openEuler-24.03-LTS:否
登录 后才可以发表评论