Messages in this thread | | | Date | Mon, 14 Feb 2011 22:46:29 +1100 | From | Dave Chinner <> | Subject | Re: [PATCH] xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1 |
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On Thu, Feb 10, 2011 at 09:25:04AM -0500, Dan Rosenberg wrote: > The FSGEOMETRY_V1 ioctl (and its compat equivalent) calls out to > xfs_fs_geometry() with a version number of 3. This code path does not > fill in the logsunit member of the passed xfs_fsop_geom_t, leading to > the leaking of four bytes of uninitialized stack data to potentially > unprivileged callers. Since all other members are filled in all code > paths and there are no padding bytes in this structure, it's safe to > avoid an expensive memset() in favor of just clearing this one field.
If this really is a security problem, then it should use a memset. This is not a performance critical path and there are differences in the padding of the structure between 32 bit and 64 bit ioctl variants (it has a compat ioctl handler) and that can only be correctly handled by memset().
Also, using a memset means we won't have the problem of introducing new uninitialised fields or padding if we ever rev the structure again...
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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