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SubjectRe: [Linux-kernel-mentees][PATCH] rtl8150: set memory to all 0xFFs on failed register reads
On Wed, Sep 16, 2020 at 10:35:40AM +0530, Anant Thazhemadam wrote:
> get_registers() copies whatever memory is written by the
> usb_control_msg() call even if the underlying urb call ends up failing.
>
> If get_registers() fails, or ends up reading 0 bytes, meaningless and
> junk register values would end up being copied over (and eventually read
> by the driver), and since most of the callers of get_registers() don't
> check the return values of get_registers() either, this would go unnoticed.
>
> It might be a better idea to try and mirror the PCI master abort
> termination and set memory to 0xFFs instead in such cases.

It would be better to use this new api call instead of
usb_control_msg():
https://lore.kernel.org/r/20200914153756.3412156-1-gregkh@linuxfoundation.org

How about porting this patch to run on top of that series instead? That
should make this logic much simpler.



>
> Fixes: https://syzkaller.appspot.com/bug?extid=abbc768b560c84d92fd3
> Reported-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
> Tested-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> ---
> drivers/net/usb/rtl8150.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
> index 733f120c852b..04fca7bfcbcb 100644
> --- a/drivers/net/usb/rtl8150.c
> +++ b/drivers/net/usb/rtl8150.c
> @@ -162,8 +162,13 @@ static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
> ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
> RTL8150_REQ_GET_REGS, RTL8150_REQT_READ,
> indx, 0, buf, size, 500);
> - if (ret > 0 && ret <= size)
> +
> + if (ret < 0)
> + memset(data, 0xff, size);
> +
> + else
> memcpy(data, buf, ret);
> +
> kfree(buf);
> return ret;
> }
> @@ -276,7 +281,7 @@ static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
>
> static inline void set_ethernet_addr(rtl8150_t * dev)
> {
> - u8 node_id[6];
> + u8 node_id[6] = {0};

This should not be needed to be done.

thanks,

greg k-h

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