Messages in this thread | | | From | Andreas Schwab <> | Subject | Re: [PATCH] avoid negative shifts in radix-tree.c, take 2 | Date | Wed, 29 Aug 2007 14:47:17 +0200 |
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Peter Lund <firefly@vax64.dk> writes:
> Shifting by more than the width of the value on the left is also not allowed.
Shifting by the width of the value is not allowed as well.
> --- linux-2.6.22/lib/radix-tree.c.orig 2007-08-27 15:42:37.000000000 +0200 > +++ linux-2.6.22/lib/radix-tree.c 2007-08-29 13:19:19.000000000 +0200 > @@ -980,12 +980,13 @@ > > static __init unsigned long __maxindex(unsigned int height) > { > - unsigned int tmp = height * RADIX_TREE_MAP_SHIFT; > - unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1; > + unsigned int width = height * RADIX_TREE_MAP_SHIFT; > + int shift = RADIX_TREE_INDEX_BITS - width; > > - if (tmp >= RADIX_TREE_INDEX_BITS) > - index = ~0UL; > - return index; > + if (shift < 0) > + return ~0UL; > + else > + return ~0UL >> shift;
Since height can be zero, you still have undefined behaviour.
Andreas.
-- Andreas Schwab, SuSE Labs, schwab@suse.de SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different." - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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