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iwlwifi: dvm: don't call << operator with a negative value 

In https://bugzilla.kernel.org/show_bug.cgi?id=177341 Bob
reported a UBSAN WARNING on rs.c.

Undefined behaviour in drivers/net/wireless/intel/iwlwifi/dvm/rs.c:746:18

This because
	i = index - 1;
	for (mask = (1 << i); i >= 0; i--, mask >>= 1)

is unsafe: i could be negative and hence we can call <<
on a negative value.
This bug doesn't have any real impact since the condition
of the for loop will prevent any usage of mask.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=177341
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
This commit is contained in:
Emmanuel Grumbach 2017-01-07 19:57:46 +02:00 committed by Luca Coelho
parent 6eac0e817a
commit 1aa0ec5cdf
1 changed files with 4 additions and 1 deletions
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5
drivers/net/wireless/intel/iwlwifi/dvm/rs.c
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@ -740,7 +740,10 @@ static u16 rs_get_adjacent_rate(struct iwl_priv *priv, u8 index, u16 rate_mask,
/* Find the previous rate that is in the rate mask */
i = index - 1;
for (mask = (1 << i); i >= 0; i--, mask >>= 1) {
if (i >= 0)
mask = BIT(i);
for (; i >= 0; i--, mask >>= 1) {
if (rate_mask & mask) {
low = i;
break;