Commit 2dc5d12b authored by Steven Rostedt's avatar Steven Rostedt
Browse files

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 <>
parent 4f3640f8
......@@ -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;
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