On 11/23/2016 05:06 PM, Nicolas Iooss wrote:
> Currently ebitmap_load() accepts loading a bitmap with highbit=192 and
> one node {startbit=0, map=0x2}. When iterating over the bitmap,
> ebitmap_for_each_bit() is expected to only yield "1" but it gives the
> following bits: 1, 65, 129.
>
> This is due to two facts in ebitmap_for_each_bit() implementation:
> * ebitmap_next() stays on the first (and only) node of the bitmap
> instead of stopping the iteration.
> * the end condition of the for loop consists in comparing the bit with
> ebitmap_length() (ie. the bitmap highbit), which is above the limit of
> the last node here.
>
> These are not bugs when the bitmap highbit is equals to
> l->startbit+MAPSIZE, where l is the last node (this is how
> ebitmap_set_bit() sets it). So a simple fix consists in making
> ebitmap_load() reject bitmaps which are loaded with an invalid highbit
> value.
>
> This issue has been found while fuzzing semodule_package with the
> American Fuzzy Lop.
Thanks, applied
>
> Signed-off-by: Nicolas Iooss <nicolas.iooss@xxxxxxx>
> ---
> libsepol/src/ebitmap.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/libsepol/src/ebitmap.c b/libsepol/src/ebitmap.c
> index fe8beb879a18..218adc293aae 100644
> --- a/libsepol/src/ebitmap.c
> +++ b/libsepol/src/ebitmap.c
> @@ -453,6 +453,12 @@ int ebitmap_read(ebitmap_t * e, void *fp)
>
> l = n;
> }
> + if (count && l->startbit + MAPSIZE != e->highbit) {
> + printf
> + ("security: ebitmap: hight bit %u has not the expected value %zu\n",
> + e->highbit, l->startbit + MAPSIZE);
> + goto bad;
> + }
>
> ok:
> rc = 0;
>
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