[PATCH] drivers/video/sis/sis_main.c: prevent readinguninitialized stack memory

From: Dan Rosenberg
Date: Wed Sep 15 2010 - 17:50:26 EST


The FBIOGET_VBLANK device ioctl allows unprivileged users to read 16
bytes of uninitialized stack memory, because the "reserved" member of
the fb_vblank struct declared on the stack is not altered or zeroed
before being copied back to the user. This patch takes care of it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>

--- linux-2.6.35.4.orig/drivers/video/sis/sis_main.c 2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/video/sis/sis_main.c 2010-09-15 11:52:41.437375730 -0400
@@ -1701,6 +1701,9 @@ static int sisfb_ioctl(struct fb_info *i
break;

case FBIOGET_VBLANK:
+
+ memset(&sisvbblank, 0, sizeof(struct fb_vblank));
+
sisvbblank.count = 0;
sisvbblank.flags = sisfb_setupvbblankflags(ivideo, &sisvbblank.vcount, &sisvbblank.hcount);





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