| From | Jiri Slaby <> | Subject | [PATCH 3.12 40/86] virtio-console: avoid DMA from stack | Date | Thu, 4 May 2017 11:04:05 +0200 |
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From: Omar Sandoval <osandov@fb.com>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
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: Jiri Slaby <jslaby@suse.cz> --- 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 15a3ec940723..55d8b073cc61 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1130,6 +1130,8 @@ 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); @@ -1138,8 +1140,14 @@ 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; } /* -- 2.12.2
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