> -----Original Message-----
> From: Intel-wired-lan <[email protected]> On Behalf
> Of Malathi
> Sent: Tuesday, August 11, 2026 7:08 AM
> To: Nguyen, Anthony L <[email protected]>; Kitszel,
> Przemyslaw <[email protected]>
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; Malathi <[email protected]>;
> [email protected]
> Subject: [Intel-wired-lan] [PATCH net-next v2] e100: fix shift-out-of-
> bounds in e100_eeprom_load()
>
> e100_eeprom_load() and e100_eeprom_save() start with an address length
> of 8 and call e100_eeprom_read() to auto-detect the real EEPROM
> address length. e100_eeprom_read() adjusts the length with
>
> *addr_len -= (i - 16);
>
> based on when the EEPROM drives a dummy zero onto EEDO. A
> malfunctioning or emulated device that drives EEDO low too early makes
> (i - 16) exceed the current length, underflowing the u16 addr_len to a
> large value such as 65529.
>
> That value is then used as a shift count:
>
> nic->eeprom_wc = 1 << addr_len;
>
> which is undefined behaviour and additionally overflows the fixed-size
> nic->eeprom[256] cache.
>
> UBSAN: shift-out-of-bounds in
> drivers/net/ethernet/intel/e100.c:768:21
> shift exponent 65529 is too large for 32-bit type 'int'
>
> The same corrupted addr_len is also fed back into e100_eeprom_read()
> for every subsequent word, where it is used as a shift count again:
>
> cmd_addr_data = ((op_read << *addr_len) | addr) << 16;
>
> so validating the length only once at the caller is not enough.
>
> Clamp the length in e100_eeprom_read() so the subtraction can never
> underflow the u16, and reject a zero or out-of-range length in
> e100_eeprom_load() and e100_eeprom_save() before using it. The EEPROM
> cache holds at most 256 words, so a valid address length is in [1, 8].
>
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=e0abb1d45ac291ebebeb
> Signed-off-by: Malathi <[email protected]>
> ---
> v2:
> - Drop the Fixes: tag and retarget to net-next; the underflow is only
> reachable with malfunctioning or emulated hardware, so this is a
> hardening change and not stable material.
> - Clamp addr_len inside e100_eeprom_read() so the auto-detect
> subtraction can never underflow the u16. The corrupted length was
> otherwise reused as a shift count for every subsequent word, so
> validating it only once at the callers (as in v1) was not enough.
> - Also reject a zero address length in e100_eeprom_load() and
> e100_eeprom_save().
>
> drivers/net/ethernet/intel/e100.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/e100.c
> b/drivers/net/ethernet/intel/e100.c
> index 29960762e64a..26a7c0aaa6e2 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;
> }
>
> @@ -765,6 +770,11 @@ 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);
> + if (!addr_len || addr_len > 8) {
> + netif_err(nic, probe, nic->netdev,
> + "invalid EEPROM address length %u\n",
> addr_len);
> + return -EINVAL;
> + }
> nic->eeprom_wc = 1 << addr_len;
>
> for (addr = 0; addr < nic->eeprom_wc; addr++) { @@ -791,6
> +801,11 @@ 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);
> + if (!addr_len || addr_len > 8) {
> + netif_err(nic, probe, nic->netdev,
> + "invalid EEPROM address length %u\n",
> addr_len);
> + return -EINVAL;
> + }
> nic->eeprom_wc = 1 << addr_len;
>
> if (start + count >= nic->eeprom_wc)
> --
> 2.43.0
Reviewed-by: Aleksandr Loktionov <[email protected]>
