linux-kernel - [PATCH 2/10] ath10k: use safer test on the result of find_first_zero

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Date:	Wed,  4 Jun 2014 11:07:52 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Kalle Valo <kvalo@....qualcomm.com>
Cc:	kernel-janitors@...r.kernel.org,
	"John W. Linville" <linville@...driver.com>,
	ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/10] ath10k: use safer test on the result of find_first_zero_bit

From: Julia Lawall <Julia.Lawall@...6.fr>

Find_first_zero_bit considers BITS_PER_LONG bits at a time, and thus may
return a larger number than the maximum position argument if that position
is not a multiple of BITS_PER_LONG.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2,e3;
statement S1,S2;
@@

e1 = find_first_zero_bit(e2,e3)
...
if (e1 
- ==
+ >=
  e3)
S1 else S2
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 drivers/net/wireless/ath/ath10k/htt_tx.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -u -p a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
--- a/drivers/net/wireless/ath/ath10k/htt_tx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
@@ -64,7 +64,7 @@ int ath10k_htt_tx_alloc_msdu_id(struct a
 
 	msdu_id = find_first_zero_bit(htt->used_msdu_ids,
 				      htt->max_num_pending_tx);
-	if (msdu_id == htt->max_num_pending_tx)
+	if (msdu_id >= htt->max_num_pending_tx)
 		return -ENOBUFS;
 
 	ath10k_dbg(ATH10K_DBG_HTT, "htt tx alloc msdu_id %d\n", msdu_id);

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