From: Omar Sandoval <osandov@osandov.com>
To: Amit Shah <amit.shah@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH] virtio-console: avoid DMA from stack
Date: Wed, 1 Feb 2017 00:02:27 -0800 [thread overview]
Message-ID: <075115ddd99246ffc4228a3e050ba68eb36c6a8c.1485935920.git.osandov@fb.com> (raw)
From: Omar Sandoval <osandov@fb.com>
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>
---
Patch based on v4.10-rc6.
drivers/char/virtio_console.c | 12 ++++++++++--
1 file 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;
}
/*
--
2.11.0
next reply other threads:[~2017-02-01 8:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-01 8:02 Omar Sandoval [this message]
2017-02-01 13:47 ` [PATCH] virtio-console: avoid DMA from stack Amit Shah
2017-03-01 20:01 ` Omar Sandoval
2017-03-01 21:25 ` Michael S. Tsirkin
2017-03-03 0:58 ` Jan Dakinevich
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