[PATCH net v2 01/10] net: systemport: Fix buffer overflow in bcm_sysport_get_stats()

[Florian Fainelli <florian.fainelli@broadcom.com>]

When running on SYSTEMPORT Lite, certain statistics are unsupported and
skipped during bcm_sysport_get_stats(). The variable 'j' tracks the
compacted index into the destination data buffer, whereas 'i' iterates
over all elements in bcm_sysport_gstrings_stats.

Because the buffer allocated by ethtool is sized only according to
bcm_sysport_get_sset_count(), storing values at data[i] instead of
data[j] writes past the allocated array bounds, leading to memory
corruption.

Fix this by writing to data[j] instead of data[i].

Fixes: 10377ba7673d ("net: systemport: Support 64bit statistics")
Assisted-by: LLM
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/ethernet/broadcom/bcmsysport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
index 4d06c6ba6641..db627cd15fb7 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -482,10 +482,10 @@ static void bcm_sysport_get_stats(struct net_device *dev,
 		    s->type == BCM_SYSPORT_STAT_NETDEV64) {
 			do {
 				start = u64_stats_fetch_begin(syncp);
-				data[i] = *(u64 *)p;
+				data[j] = *(u64 *)p;
 			} while (u64_stats_fetch_retry(syncp, start));
 		} else
-			data[i] = *(u32 *)p;
+			data[j] = *(u32 *)p;
 		j++;
 	}
 
-- 
2.34.1