Re: [PATCH][next] scsi: lpfc: fix less than zero comparison on unsigned int computation

From: James Smart
Date: Mon Jul 06 2020 - 10:48:24 EST



On 7/6/2020 6:08 AM, Colin King wrote:
From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

The expressions start_idx - dbg_cnt is evaluated using unsigned int
arthithmetic (since these variables are unsigned ints) and hence can
never be less than zero, so the less than comparison is never true.
Re-write the expression to check for start_idx being less than dbg_cnt.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: 372c187b8a70 ("scsi: lpfc: Add an internal trace log buffer")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
---
drivers/scsi/lpfc/lpfc_init.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/lpfc/lpfc_init.c b/drivers/scsi/lpfc/lpfc_init.c
index 7285b0114837..ce5afe7b11d0 100644
--- a/drivers/scsi/lpfc/lpfc_init.c
+++ b/drivers/scsi/lpfc/lpfc_init.c
@@ -14152,7 +14152,7 @@ void lpfc_dmp_dbg(struct lpfc_hba *phba)
if ((start_idx + dbg_cnt) > (DBG_LOG_SZ - 1)) {
temp_idx = (start_idx + dbg_cnt) % DBG_LOG_SZ;
} else {
- if ((start_idx - dbg_cnt) < 0) {
+ if (start_idx < dbg_cnt) {
start_idx = DBG_LOG_SZ - (dbg_cnt - start_idx);
temp_idx = 0;
} else {

Thanks Colin - I was about to send a patch for this. Has this fix and one a couple of lines further down. I will post it shortly.

-- james