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Date:   Tue, 10 Oct 2023 21:24:42 +0000
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Message-ID: <20231010-strncpy-drivers-net-ethernet-marvell-mvpp2-mvpp2_main-c-v1-1-51be96ad0324@google.com>
Subject: [PATCH] net: mvpp2: replace deprecated strncpy with strscpy
From:   Justin Stitt <justinstitt@google.com>
To:     Marcin Wojtas <mw@semihalf.com>,
        Russell King <linux@armlinux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org,
        Justin Stitt <justinstitt@google.com>
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Precedence: bulk

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect `irqname` to be NUL-terminated based on its use with
of_irq_get_byname() -> of_property_match_string() wherein it is used
with a format string and a `strcmp`:
|       pr_debug("comparing %s with %s\n", string, p);
|       if (strcmp(string, p) == 0)
|               return i; /* Found it; return index */

NUL-padding is not required as is evident by other assignments to
`irqname` which do not NUL-pad:
|       if (port->flags & MVPP2_F_DT_COMPAT)
|               snprintf(irqname, sizeof(irqname), "tx-cpu%d", i);
|       else
|               snprintf(irqname, sizeof(irqname), "hif%d", i);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 21c3f9b015c8..331dba2ae13d 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -5831,7 +5831,7 @@ static int mvpp2_multi_queue_vectors_init(struct mvpp2_port *port,
 			v->type = MVPP2_QUEUE_VECTOR_SHARED;
 
 			if (port->flags & MVPP2_F_DT_COMPAT)
-				strncpy(irqname, "rx-shared", sizeof(irqname));
+				strscpy(irqname, "rx-shared", sizeof(irqname));
 		}
 
 		if (port_node)

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231010-strncpy-drivers-net-ethernet-marvell-mvpp2-mvpp2_main-c-e9743cf1cf8f

Best regards,
--
Justin Stitt <justinstitt@google.com>