2020-07-06 13:11:50

by Colin King

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

From: Colin Ian King <[email protected]>

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 <[email protected]>
---
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 {
--
2.27.0

2020-07-06 14:51:22

by James Smart

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

On 7/6/2020 6:08 AM, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> 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 <[email protected]>
> ---
> 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