Re: [Intel-wired-lan] [PATCH] e100: prevent shift out-of-bounds in e100_eeprom_load

[Yalagada Pavan Kumar <pavankumaryalagada@gmail.com>]

On Sun, Aug 09, 2026 at 12:12:31AM +0900, Kohei Enju wrote:
> On 08/07 20:26, pavankumaryalagada@gmail.com wrote:
> > From: Yalagada Pavan Kumar <pavankumaryalagada@gmail.com>
> > 
> > When reading the EEPROM address length, e100_eeprom_read() can return
> > an invalid length (0 or >= 16). Passing an invalid addr_len to bit-shift
> > operations causes a shift out-of-bounds, triggering a kernel panic or
> > UBSAN warning.
> > 
> > Validate addr_len after reading it from EEPROM and return -EINVAL if
> > the value is out of bounds. Additionally, use 1U to prevent
> > signed integer overflow when calculating eeprom_wc.
> > 
> > Reported-by: syzbot+e0abb1d45ac291ebebeb@syzkaller.appspotmail.com
> > Tested-by: syzbot+e0abb1d45ac291ebebeb@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=e0abb1d45ac291ebebeb
> > Signed-off-by: Yalagada Pavan Kumar <pavankumaryalagada@gmail.com>
> > ---
> > Tested using syzbot c reproducer.
> > ---
> >  drivers/net/ethernet/intel/e100.c | 17 +++++++++++++++--
> >  1 file changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/e100.c b/drivers/net/ethernet/intel/e100.c
> > index 29960762e64a..1de5cd41ea0c 100644
> > --- a/drivers/net/ethernet/intel/e100.c
> > +++ b/drivers/net/ethernet/intel/e100.c
> > @@ -744,7 +744,12 @@ static __le16 e100_eeprom_read(struct nic *nic, u16 *addr_len, u16 addr)
> >  		 * complete address.  Use this to adjust addr_len. */
> >  		ctrl = ioread8(&nic->csr->eeprom_ctrl_lo);
> >  		if (!(ctrl & eedo) && i > 16) {
> > -			*addr_len -= (i - 16);
> > +			u16 len = i - 16;
> > +
> > +			if (len > *addr_len)
> > +				*addr_len = 0;
> > +			else
> > +				*addr_len -= len;
> >  			i = 17;
> >  		}
> >  
> > @@ -765,7 +770,15 @@ static int e100_eeprom_load(struct nic *nic)
> >  
> >  	/* Try reading with an 8-bit addr len to discover actual addr len */
> >  	e100_eeprom_read(nic, &addr_len, 0);
> > -	nic->eeprom_wc = 1 << addr_len;
> > +
> > +	if (!addr_len || addr_len >= 16) {
> > +		netif_err(nic, probe, nic->netdev,
> > +			"Invalid EEPROM address length %u\n",
> > +			addr_len);
> > +		return -EINVAL;
> 
> An invalid address length here appears to indicate an unexpected
> response from the EEPROM, rather than an invalid argument. Therefore,
> -EINVAL seems somewhat misleading. Would -EIO be more appropriate here?
Agreed, addr_len comes from an unexpected EEPROM response,
so i will change -EINVAL to -EIO.
> 
> Also, e100_eeprom_save() seems to have the same pattern. Shouldn't we
> fix that as well?
yes, i'll fix e100_eeprom_save() as well. 
> 
> > +	}
> > +
> > +	nic->eeprom_wc = 1U << addr_len;
> 
> The commit message says that the U suffix prevents signed integer
> overflow. However, after the validation addr_len is in [1, 15], so 1 <<
> addr_len cannot overflow an int. I think what prevents the out-of-bounds
> shift is the validation, not the U.
Agreed, I'll remove the unnecessary U suffix.
I made these changes and will send v2.
> 
> >  
> >  	for (addr = 0; addr < nic->eeprom_wc; addr++) {
> >  		nic->eeprom[addr] = e100_eeprom_read(nic, &addr_len, addr);
> > -- 
> > 2.43.0
> >