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btrfs-progs: Fix undefined behavior in radix-tree.c.

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When running with UndefinedBehaviorSanitizer, the tests produce the following
error:

  radix-tree.c:836:30: runtime error: shift exponent 18446744073709551613
  is too large for 64-bit type 'unsigned long'

(That's a negative shift exponent represented as an unsigned long.)

Even though the value is discarded in those cases, it's still undefined
behavior; see the C99 standard, section 6.5.7, paragraph three: "If the
value of the right operand is negative [...] the behavior is undefined."

Signed-off-by: Adam Buchbinder <abuchbinder@google.com>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Adam Buchbinder 2014-06-13 14:18:50 -07:00 committed by David Sterba
parent 5351d29eef
commit c9951e2269
1 changed files with 3 additions and 3 deletions
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6
radix-tree.c
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@ -833,10 +833,10 @@ int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
static 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 long index = ~0UL;
if (tmp >= RADIX_TREE_INDEX_BITS)
index = ~0UL;
if (tmp < RADIX_TREE_INDEX_BITS)
index = (index >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
return index;
}