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Commit 2dc5d12b authored by Steven Rostedt's avatar Steven Rostedt
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tracing: do not return EFAULT if read copied anything 



Impact: fix trace read to conform to standards

Andrew Morton, Theodore Tso and H. Peter Anvin brought to my attention
that a userspace read should not return -EFAULT if it succeeded in
copying anything. It should only return -EFAULT if it failed to copy
at all.

This patch modifies the check of copy_from_user and updates the return
code appropriately.

I also used H. Peter Anvin's short cut rule to just test ret == count.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 4f3640f8

kernel/trace/trace.c

+12 −2
Original line number Diff line number Diff line
@@ -346,6 +346,9 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt) 
	int len;

	int ret;



	if (!cnt)

		return 0;



	if (s->len <= s->readpos)

		return -EBUSY;
@@ -353,9 +356,11 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt) 
	if (cnt > len)

		cnt = len;

	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);

	if (ret)

	if (ret == cnt)

		return -EFAULT;



	cnt -= ret;



	s->readpos += len;

	return cnt;

}
@@ -3049,6 +3054,9 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
	ssize_t ret;

	size_t size;



	if (!count)

		return 0;



	/* Do we have previous read data to read? */

	if (info->read < PAGE_SIZE)

		goto read;
@@ -3073,8 +3081,10 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
		size = count;



	ret = copy_to_user(ubuf, info->spare + info->read, size);

	if (ret)

	if (ret == size)

		return -EFAULT;

	size -= ret;



	*ppos += size;

	info->read += size;