Re: [PATCH net] net: dsa: mv88e6xxx: Avoid uninitialized value on MDIO read error
Andrew Lunn <[email protected]>
| Newsgroups | org.kernel.vger.netdev,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On Fri, Aug 14, 2026 at 09:40:06PM +0800, Ruoyu Wang wrote:
> An SMI timeout or PPU access failure can make a Clause 22 PHY read
> return without initializing its output value. When reading MII_PHYSID2,
> mv88e6xxx_mdio_read() still passes that value through the internal PHY
> model-number workaround before returning the error, causing an
> uninitialized stack read.
>
> Run the workaround only after a successful PHY read. This preserves the
> original error and leaves successful PHY ID reads unchanged.
>
> This issue was found by a static analysis checker and confirmed by
> manual source review.
>
> Fixes: da9f33018e2c ("net: dsa: mv88e6xxx: Workaround missing PHY ID on mv88e6390")
> Signed-off-by: Ruoyu Wang <[email protected]>
> ---
> drivers/net/dsa/mv88e6xxx/chip.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index 80b877c74513d..e71707ce71cbc 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -3770,7 +3770,7 @@ static int mv88e6xxx_mdio_read(struct mii_bus *bus, int phy, int reg)
> mv88e6xxx_reg_unlock(chip);
>
> /* Some internal PHYs don't have a model number. */
> - if (reg == MII_PHYSID2 && !(val & 0x3f0) &&
> + if (!err && reg == MII_PHYSID2 && !(val & 0x3f0) &&
> chip->info->family < ARRAY_SIZE(family_prod_id_table)) {
> prod_id = family_prod_id_table[chip->info->family];
> if (prod_id)
Ugly.
Please do the usual for checking for errors and returning.
Also, this is not worthy of stable, please drop the Fixes tag, and
post to net-next.
Andrew