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authorOmar Sandoval <osandov@fb.com>2017-02-01 00:02:27 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-04-21 09:32:42 +0200
commite5349c13c7a8bd6e0be0f81f4464fc2edae05d5b (patch)
parente0116f4d9a9ad5112d315b236c7b3d7036d404d7 (diff)
virtio-console: avoid DMA from stack
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>
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 17857beb4892..3cbf4c95e446 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1136,6 +1136,8 @@ static int put_chars(u32 vtermno, const char *buf, int count)
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 char *buf, int count)
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;