[PATCH 4.9 50/51] pstore: Convert console write to use ->write_buf

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 70ad35db3321a6d129245979de4ac9d06eed897c ]

Maybe I'm missing something, but I don't know why it needs to copy the
input buffer to psinfo->buf and then write.  Instead we can write the
input buffer directly.  The only implementation that supports console
message (i.e. ramoops) already does it for ftrace messages.

For the upcoming virtio backend driver, it needs to protect psinfo->buf
overwritten from console messages.  If it could use ->write_buf method
instead of ->write, the problem will be solved easily.

Cc: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Namhyung Kim <namhy...@kernel.org>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 fs/pstore/platform.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -584,8 +584,8 @@ static void pstore_console_write(struct
                } else {
                        spin_lock_irqsave(&psinfo->buf_lock, flags);
                }
-               memcpy(psinfo->buf, s, c);
-               psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
+               psinfo->write_buf(PSTORE_TYPE_CONSOLE, 0, &id, 0,
+                                 s, 0, c, psinfo);
                spin_unlock_irqrestore(&psinfo->buf_lock, flags);
                s += c;
                c = e - s;