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virtio-console: avoid DMA from stack 

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>
This commit is contained in:
Omar Sandoval 2017-02-01 00:02:27 -08:00 committed by Michael S. Tsirkin
parent f889491380
commit c4baad5029
1 changed files with 10 additions and 2 deletions
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12
drivers/char/virtio_console.c
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@ -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;
}
/*