From: Ye Bin <yebin10@huawei.com>
To: <axboe@kernel.dk>, <rostedt@goodmis.org>, <mhiramat@kernel.org>,
<linux-block@vger.kernel.org>
Cc: <linux-kernel@vger.kernel.org>, Ye Bin <yebin10@huawei.com>
Subject: [PATCH -next 2/3] blktrace: fix possible memleak in '__blk_trace_remove'
Date: Mon, 17 Oct 2022 14:53:20 +0800 [thread overview]
Message-ID: <20221017065321.2846017-3-yebin10@huawei.com> (raw)
In-Reply-To: <20221017065321.2846017-1-yebin10@huawei.com>
When test as follows:
step1: ioctl(sda, BLKTRACESETUP, &arg)
step2: ioctl(sda, BLKTRACESTART, NULL)
step3: ioctl(sda, BLKTRACETEARDOWN, NULL)
step4: ioctl(sda, BLKTRACESETUP, &arg)
Got issue as follows:
debugfs: File 'dropped' in directory 'sda' already present!
debugfs: File 'msg' in directory 'sda' already present!
debugfs: File 'trace0' in directory 'sda' already present!
And also find syzkaller report issue like "KASAN: use-after-free Read in relay_switch_subbuf"
"https://syzkaller.appspot.com/bug?id=13849f0d9b1b818b087341691be6cc3ac6a6bfb7"
If remove block trace without stop(BLKTRACESTOP) block trace, '__blk_trace_remove'
will just set 'q->blk_trace' with NULL. However, debugfs file isn't removed, so
will report file already present when call BLKTRACESETUP.
static int __blk_trace_remove(struct request_queue *q)
{
struct blk_trace *bt;
bt = rcu_replace_pointer(q->blk_trace, NULL,
lockdep_is_held(&q->debugfs_mutex));
if (!bt)
return -EINVAL;
if (bt->trace_state != Blktrace_running)
blk_trace_cleanup(q, bt);
return 0;
}
If do test as follows:
step1: ioctl(sda, BLKTRACESETUP, &arg)
step2: ioctl(sda, BLKTRACESTART, NULL)
step3: ioctl(sda, BLKTRACETEARDOWN, NULL)
step4: remove sda
There will remove debugfs directory which will remove recursively all file
under directory.
>> blk_release_queue
>> debugfs_remove_recursive(q->debugfs_dir)
So all files which created in 'do_blk_trace_setup' are removed, and
'dentry->d_inode' is NULL. But 'q->blk_trace' is still in 'running_trace_lock',
'trace_note_tsk' will traverse 'running_trace_lock' all nodes.
>>trace_note_tsk
>> trace_note
>> relay_reserve
>> relay_switch_subbuf
>> d_inode(buf->dentry)->i_size
To solve above issues, reference commit '5afedf670caf', first stop block trace
when block trace state is 'Blktrace_running' in '__blk_trace_remove'.
Signed-off-by: Ye Bin <yebin10@huawei.com>
---
kernel/trace/blktrace.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index edd83e213580..0d93a0110ab5 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -395,8 +395,10 @@ static int __blk_trace_remove(struct request_queue *q)
if (!bt)
return -EINVAL;
- if (bt->trace_state != Blktrace_running)
- blk_trace_cleanup(q, bt);
+ if (bt->trace_state == Blktrace_running)
+ blk_trace_switch_state(bt, 0);
+
+ blk_trace_cleanup(q, bt);
return 0;
}
--
2.31.1
next prev parent reply other threads:[~2022-10-17 6:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-17 6:53 [PATCH -next 0/3] fix possible memleak in '__blk_trace_remove' Ye Bin
2022-10-17 6:53 ` [PATCH -next 1/3] blktrace: introduce 'blk_trace_swicth_state' helper Ye Bin
2022-10-18 7:40 ` Christoph Hellwig
2022-10-17 6:53 ` Ye Bin [this message]
2022-10-18 7:38 ` [PATCH -next 2/3] blktrace: fix possible memleak in '__blk_trace_remove' Yu Kuai
2022-10-18 7:41 ` Christoph Hellwig
2022-10-17 6:53 ` [PATCH -next 3/3] blktrace: remove unnessary stop block trace in 'blk_trace_shutdown' Ye Bin
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