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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>