tracing: do not return EFAULT if read copied anything (2dc5d12b) · Commits · 戴 / test

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:

Steven Rostedt <srostedt@redhat.com>

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 @@ read:
		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;

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