lkml.org 
[lkml]   [2017]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.18 059/124] virtio-console: avoid DMA from stack
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

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

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
@@ -1129,6 +1129,8 @@ 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);
@@ -1137,8 +1139,14 @@ 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;
}

/*

\
 
 \ /
  Last update: 2017-04-20 08:59    [W:0.612 / U:2.272 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site