[ Upstream commit c68b2c9eba38ec3f60f4894b189090febf4d8d22 ]
The MII code does not check the return value of mdio_read (among
others), and therefore no error code should be sent. A previous fix to
the use of an uninitialized variable propagates negative error codes,
that might lead to wrong operations by the MII library.
An example of such issues is the use of mii_nway_restart by the dm9601
driver. The mii_nway_restart function does not check the value returned
by mdio_read, which in this case might be a negative number which could
contain the exact bit the function checks (BMCR_ANENABLE = 0x1000).
Return zero in case of error, as it is common practice in users of
mdio_read to avoid wrong uses of the return value.
Fixes: 8f8abb863fa5 ("net: usb: dm9601: fix uninitialized variable use in dm9601_mdio_read")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Peter Korsgaard <peter@korsgaard.com>
Link: https://lore.kernel.org/r/20240225-dm9601_ret_err-v1-1-02c1d959ea59@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 8f8abb863fa5a4cc18955c6a0e17af0ded3e4a76 upstream.
syzbot has found an uninit-value bug triggered by the dm9601 driver [1].
This error happens because the variable res is not updated if the call
to dm_read_shared_word returns an error. In this particular case -EPROTO
was returned and res stayed uninitialized.
This can be avoided by checking the return value of dm_read_shared_word
and propagating the error if the read operation failed.
[1] https://syzkaller.appspot.com/bug?extid=1f53a30781af65d2c955
Cc: stable@vger.kernel.org
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reported-and-tested-by: syzbot+1f53a30781af65d2c955@syzkaller.appspotmail.com
Acked-by: Peter Korsgaard <peter@korsgaard.com>
Fixes: d0374f4f9c35cdfbee0 ("USB: Davicom DM9601 usbnet driver")
Link: https://lore.kernel.org/r/20231009-topic-dm9601_uninit_mdio_read-v2-1-f2fe39739b6c@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
