Description of problem:
The FBIOGET_VBLANK device ioctl in sis_main.c 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.
Red Hat would like to thank Dan Rosenberg for reporting this issue.
This issue did not affect the versions of Linux kernel as shipped with Red Hat
Enterprise Linux 3, 4, 5, and Red Hat Enterprise MRG as they did not include
or support the affected functionality.