Re: [PATCH] drivers/video/via/ioctl.c: prevent reading uninitializedstack memory
From: Florian Tobias Schandinat
Date: Wed Sep 15 2010 - 18:42:27 EST
Hi,
Dan Rosenberg schrieb:
The VIAFB_GET_INFO device ioctl allows unprivileged users to read 1968
bytes of uninitialized stack memory, because the "reserved" member of
the viafb_ioctl_info struct declared on the stack is not altered or
zeroed before being copied back to the user. This patch takes care of
it.
I am wondering about the number of bytes as sizeof(struct viafb_ioctl_info) =
256 so it should be a bit less. But that's just nitpicking, the issue is
certainly real. Your patch does the right thing but there is a bug in it:
Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
--- linux-2.6.35.4.orig/drivers/video/via/ioctl.c 2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/video/via/ioctl.c 2010-09-15 11:53:29.997375748 -0400
@@ -25,6 +25,8 @@ int viafb_ioctl_get_viafb_info(u_long ar
{
struct viafb_ioctl_info viainfo;
+ memset(&viainfo, 0, sizeof(struct viafb_ioctl));
Shouldn't it be sizeof(struct viafb_ioctl_info) or sizeof(viainfo) ?
At least here it does not even compile otherwise....
Thanks,
Florian Tobias Schandinat
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