[PATCH v3] igb: Fix string truncation warnings in igb_set_fw_version

[Kunwu Chan]

Commit 1978d3ead82c ("intel: fix string truncation warnings")
fixes '-Wformat-truncation=' warnings in igb_main.c by using kasprintf.

drivers/net/ethernet/intel/igb/igb_main.c:3092:53: warning：‘%d’ directive output may be truncated writing between 1 and 5 bytes into a region of size between 1 and 13 [-Wformat-truncation=]
 3092 |                                  "%d.%d, 0x%08x, %d.%d.%d",
      |                                                     ^~
drivers/net/ethernet/intel/igb/igb_main.c:3092:34: note：directive argument in the range [0, 65535]
 3092 |                                  "%d.%d, 0x%08x, %d.%d.%d",
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/igb/igb_main.c:3092:34: note：directive argument in the range [0, 65535]
drivers/net/ethernet/intel/igb/igb_main.c:3090:25: note：‘snprintf’ output between 23 and 43 bytes into a destination of size 32

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

Fix this warning by using a larger space for adapter->fw_version,
and then fall back and continue to use snprintf.

Fixes: 1978d3ead82c ("intel: fix string truncation warnings")
Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
Cc: Kunwu Chan <kunwu.chan@xxxxxxxxxxx>
Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
---
v2: Fall back to use snprintf and a larger space,as suggested by
https://lore.kernel.org/all/20231212132637.1b0fb8aa@xxxxxxxxxx/
v3: Add detailed warnings to the commit msg ,no functional change
---
 drivers/net/ethernet/intel/igb/igb.h      |  2 +-
 drivers/net/ethernet/intel/igb/igb_main.c | 35 ++++++++++++-----------
 2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index a2b759531cb7..3c2dc7bdebb5 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -637,7 +637,7 @@ struct igb_adapter {
 		struct timespec64 period;
 	} perout[IGB_N_PEROUT];
 
-	char fw_version[32];
+	char fw_version[48];
 #ifdef CONFIG_IGB_HWMON
 	struct hwmon_buff *igb_hwmon_buff;
 	bool ets;
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index b2295caa2f0a..ce762d77d2c1 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3069,7 +3069,6 @@ void igb_set_fw_version(struct igb_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
 	struct e1000_fw_version fw;
-	char *lbuf;
 
 	igb_get_fw_version(hw, &fw);
 
@@ -3077,34 +3076,36 @@ void igb_set_fw_version(struct igb_adapter *adapter)
 	case e1000_i210:
 	case e1000_i211:
 		if (!(igb_get_flash_presence_i210(hw))) {
-			lbuf = kasprintf(GFP_KERNEL, "%2d.%2d-%d",
-					 fw.invm_major, fw.invm_minor,
-					 fw.invm_img_type);
+			snprintf(adapter->fw_version,
+				 sizeof(adapter->fw_version),
+				 "%2d.%2d-%d",
+				 fw.invm_major, fw.invm_minor,
+				 fw.invm_img_type);
 			break;
 		}
 		fallthrough;
 	default:
 		/* if option rom is valid, display its version too */
 		if (fw.or_valid) {
-			lbuf = kasprintf(GFP_KERNEL, "%d.%d, 0x%08x, %d.%d.%d",
-					 fw.eep_major, fw.eep_minor,
-					 fw.etrack_id, fw.or_major, fw.or_build,
-					 fw.or_patch);
+			snprintf(adapter->fw_version,
+				 sizeof(adapter->fw_version),
+				 "%d.%d, 0x%08x, %d.%d.%d",
+				 fw.eep_major, fw.eep_minor, fw.etrack_id,
+				 fw.or_major, fw.or_build, fw.or_patch);
 		/* no option rom */
 		} else if (fw.etrack_id != 0X0000) {
-			lbuf = kasprintf(GFP_KERNEL, "%d.%d, 0x%08x",
-					 fw.eep_major, fw.eep_minor,
-					 fw.etrack_id);
+			snprintf(adapter->fw_version,
+				 sizeof(adapter->fw_version),
+				 "%d.%d, 0x%08x",
+				 fw.eep_major, fw.eep_minor, fw.etrack_id);
 		} else {
-			lbuf = kasprintf(GFP_KERNEL, "%d.%d.%d", fw.eep_major,
-					 fw.eep_minor, fw.eep_build);
+			snprintf(adapter->fw_version,
+				 sizeof(adapter->fw_version),
+				 "%d.%d.%d",
+				 fw.eep_major, fw.eep_minor, fw.eep_build);
 		}
 		break;
 	}
-
-	/* the truncate happens here if it doesn't fit */
-	strscpy(adapter->fw_version, lbuf, sizeof(adapter->fw_version));
-	kfree(lbuf);
 }
 
 /**
-- 
2.39.2