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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Malathi , syzbot+e0abb1d45ac291ebebeb@syzkaller.appspotmail.com Subject: [PATCH] e100: fix shift-out-of-bounds in e100_eeprom_load() Date: Mon, 10 Aug 2026 09:07:46 +0000 Message-ID: <20260810090746.206290-1-malathi.a2000@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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]. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+e0abb1d45ac291ebebeb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=e0abb1d45ac291ebebeb Signed-off-by: Malathi 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