Re: [PATCH net-next v6 8/9] net: dsa: lan9645x: add mdb management

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The `mac` array on the stack in `lan9645x_mdb_update_dest()` is passed to `ether_addr_copy()`, which strictly requires 2-byte alignment.
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commit 96e0068b5c80a051af89df2214f42e04d526551d
Author: Jens Emil Schulz Østergaard <jensemil.schulzostergaard@microchip.com>
net: dsa: lan9645x: add mdb management

Add support for dsa mdb callbacks. L2 multicast and IP multicast is
handled differently. IP multicast stores the port group mask inline in
the mac table.

> diff --git a/drivers/net/dsa/microchip/lan9645x/lan9645x_mdb.c b/drivers/net/dsa/microchip/lan9645x/lan9645x_mdb.c
> new file mode 100644
> index 0000000000000..0ba3e0974dc08
> --- /dev/null
> +++ b/drivers/net/dsa/microchip/lan9645x/lan9645x_mdb.c

[ ... ]

> +static int lan9645x_mdb_update_dest(struct lan9645x *lan9645x,
> +				    struct lan9645x_mdb_entry *mdb_entry,
> +				    enum macaccess_entry_type type,
> +				    struct lan9645x_pgid_entry *new_pgid,
> +				    u16 new_ports)
> +{
> +	struct lan9645x_pgid_entry *old_pgid;
> +	unsigned char mac[ETH_ALEN];

[Severity: High]
Could this stack variable be placed at an odd alignment by the compiler?

The mac array is passed to lan9645x_mdb_encode_mac(), which uses
ether_addr_copy() to copy the MAC address. The ether_addr_copy() function
strictly requires both pointers to be 16-bit aligned.

On architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS,
ether_addr_copy() casts the pointers to u16 * and dereferences them.
Dereferencing an unaligned pointer can trigger an unaligned memory access
exception and lead to a kernel oops.

> +	int err, pgid_index;
> +	bool cpu_copy;
> +
> +	old_pgid = mdb_entry->pgid;
> +	lan9645x_mdb_encode_mac(mac, mdb_entry->mac, new_ports, type);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260527-dsa_lan9645x_switch_driver_base-v6-0-4d409ae64f3c@microchip.com?part=8