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Commit 86c6667f authored by Omar Sandoval's avatar Omar Sandoval Committed by Greg Kroah-Hartman
Browse files

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: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarAmit Shah <amit.shah@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Brad Spengler <spender@grsecurity.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fb003193

drivers/char/virtio_console.c

+10 −2
Original line number Diff line number Diff line
@@ -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;

}



/*