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virtio-console: avoid DMA from stack

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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 <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Amit Shah <[email protected]>
This commit is contained in:
Omar Sandoval authored and Michael S. Tsirkin committed 2017-03-02 01:35:06 +02:00
1 parent f889491380
commit c4baad5029
1 file changed
+10 -2
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drivers/char/virtio_console.c
+10 -2
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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;
}
/*