RE: [PATCH iwl-next v4] e100: prevent shift-out-of-bounds in EEPROM access

[Loktionov, Aleksandr]

> -----Original Message-----
> From: pavankumaryalagada@xxxxxxxxx <pavankumaryalagada@xxxxxxxxx>
> Sent: Thursday, August 20, 2026 11:41 AM
> To: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel,
> Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>
> Cc: intel-wired-lan@xxxxxxxxxxxxxxxx; Andrew Lunn
> <andrew+netdev@xxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; Eric
> Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; skhan@xxxxxxxxxxxxxxxxxxx;
> syzbot+e0abb1d45ac291ebebeb@xxxxxxxxxxxxxxxxxxxxxxxxx; kohei@xxxxxxxx;
> Loktionov, Aleksandr <aleksandr.loktionov@xxxxxxxxx>; Yalagada Pavan
> Kumar <pavankumaryalagada@xxxxxxxxx>
> Subject: [PATCH iwl-next v4] e100: prevent shift-out-of-bounds in
> EEPROM access
> 
> From: Yalagada Pavan Kumar <pavankumaryalagada@xxxxxxxxx>
> 
> When reading the EEPROM address length, e100_eeprom_read() can return
> an invalid length. This value is then used as a shift count when
> calculating eeprom_wc, resulting in a shift-out-of-bounds UBSAN
> warning.
> 
> Stop EEPROM address probing if the detected address length exceeds the
> initial address length to prevent addr_len from underflowing.
> 
> Validate addr_len after reading it from the EEPROM in both
> e100_eeprom_load() and e100_eeprom_save(), and return -EIO if the
> value is zero or greater than 8.
> 
> Reported-by: syzbot+e0abb1d45ac291ebebeb@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=e0abb1d45ac291ebebeb
> Signed-off-by: Yalagada Pavan Kumar <pavankumaryalagada@xxxxxxxxx>
> ---
> 
> v4:
>  - Squash the v1-v3 changes into a single standalone patch.
>  - Prevent addr_len underflow during EEPROM probing.
>  - Validate addr_len in e100_eeprom_load() and e100_eeprom_save().
>  - Use BIT() and cast the result to u16 for eeprom_wc.
>  - Target iwl-next as requested by Tony Nguyen.
> 
> v3: https://lore.kernel.org/all/20260816113754.22900-1-
> pavankumaryalagada@xxxxxxxxx/T/
> 
> v2: https://lore.kernel.org/all/20260810083355.21631-1-
> pavankumaryalagada@xxxxxxxxx/T/
> 
> v1: https://lore.kernel.org/all/20260807145626.52692-1-
> pavankumaryalagada@xxxxxxxxx/T/
> ---
>  drivers/net/ethernet/intel/e100.c | 29 ++++++++++++++++++++++++++---
>  1 file changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e100.c
> b/drivers/net/ethernet/intel/e100.c
> index 29960762e64a..cd8190386652 100644
> --- a/drivers/net/ethernet/intel/e100.c
> +++ b/drivers/net/ethernet/intel/e100.c
> @@ -744,7 +744,14 @@ 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;
> +				break;
> +			}
> +
> +			*addr_len -= len;
>  			i = 17;
>  		}
> 
> @@ -765,7 +772,15 @@ 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 > 8) {
> +		netif_err(nic, probe, nic->netdev,
> +			  "Invalid EEPROM address length %u\n",
> +			  addr_len);
> +		return -EIO;
> +	}
> +
> +	nic->eeprom_wc = (u16)BIT(addr_len);
> 
>  	for (addr = 0; addr < nic->eeprom_wc; addr++) {
>  		nic->eeprom[addr] = e100_eeprom_read(nic, &addr_len,
> addr); @@ -791,7 +806,15 @@ static int e100_eeprom_save(struct nic
> *nic, u16 start, u16 count)
> 
>  	/* 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 > 8) {
> +		netif_err(nic, probe, nic->netdev,
> +			  "Invalid EEPROM address length %u\n",
> +			  addr_len);
> +		return -EIO;
> +	}
> +
> +	nic->eeprom_wc = (u16)BIT(addr_len);
> 
>  	if (start + count >= nic->eeprom_wc)
>  		return -EINVAL;
> --
> 2.43.0

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>