| From c4baad50297d84bde1a7ad45e50c73adae4a2192 Mon Sep 17 00:00:00 2001 |
| From: Omar Sandoval <osandov@fb.com> |
| Date: Wed, 1 Feb 2017 00:02:27 -0800 |
| Subject: virtio-console: avoid DMA from stack |
| |
| From: Omar Sandoval <osandov@fb.com> |
| |
| commit c4baad50297d84bde1a7ad45e50c73adae4a2192 upstream. |
| |
| put_chars() stuffs the buffer it gets into an sg, but that buffer may be |
| on the stack. This breaks with CONFIG_VMAP_STACK=y (for me, it |
| manifested as printks getting turned into NUL bytes). |
| |
| Signed-off-by: Omar Sandoval <osandov@fb.com> |
| Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
| Reviewed-by: Amit Shah <amit.shah@redhat.com> |
| Cc: Ben Hutchings <ben@decadent.org.uk> |
| Cc: Brad Spengler <spender@grsecurity.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/char/virtio_console.c | 12 ++++++++++-- |
| 1 file changed, 10 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/char/virtio_console.c |
| +++ b/drivers/char/virtio_console.c |
| @@ -1136,6 +1136,8 @@ static int put_chars(u32 vtermno, const |
| { |
| struct port *port; |
| struct scatterlist sg[1]; |
| + void *data; |
| + int ret; |
| |
| if (unlikely(early_put_chars)) |
| return early_put_chars(vtermno, buf, count); |
| @@ -1144,8 +1146,14 @@ static int put_chars(u32 vtermno, const |
| if (!port) |
| return -EPIPE; |
| |
| - sg_init_one(sg, buf, count); |
| - return __send_to_port(port, sg, 1, count, (void *)buf, false); |
| + data = kmemdup(buf, count, GFP_ATOMIC); |
| + if (!data) |
| + return -ENOMEM; |
| + |
| + sg_init_one(sg, data, count); |
| + ret = __send_to_port(port, sg, 1, count, data, false); |
| + kfree(data); |
| + return ret; |
| } |
| |
| /* |
