linux-kernel - [PATCH 5.15 137/172] eeprom: ee1004: limit i2c reads to I2C_SMBUS_BLOCK

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Message-Id: <20220214092511.131823707@linuxfoundation.org>
Date:   Mon, 14 Feb 2022 10:26:35 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Jonas Malaco <jonas@...tocubo.io>
Subject: [PATCH 5.15 137/172] eeprom: ee1004: limit i2c reads to I2C_SMBUS_BLOCK_MAX

From: Jonas Malaco <jonas@...tocubo.io>

commit c0689e46be23160d925dca95dfc411f1a0462708 upstream.

Commit effa453168a7 ("i2c: i801: Don't silently correct invalid transfer
size") revealed that ee1004_eeprom_read() did not properly limit how
many bytes to read at once.

In particular, i2c_smbus_read_i2c_block_data_or_emulated() takes the
length to read as an u8.  If count == 256 after taking into account the
offset and page boundary, the cast to u8 overflows.  And this is common
when user space tries to read the entire EEPROM at once.

To fix it, limit each read to I2C_SMBUS_BLOCK_MAX (32) bytes, already
the maximum length i2c_smbus_read_i2c_block_data_or_emulated() allows.

Fixes: effa453168a7 ("i2c: i801: Don't silently correct invalid transfer size")
Cc: stable@...r.kernel.org
Reviewed-by: Heiner Kallweit <hkallweit1@...il.com>
Signed-off-by: Jonas Malaco <jonas@...tocubo.io>
Link: https://lore.kernel.org/r/20220203165024.47767-1-jonas@protocubo.io
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/misc/eeprom/ee1004.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/misc/eeprom/ee1004.c
+++ b/drivers/misc/eeprom/ee1004.c
@@ -114,6 +114,9 @@ static ssize_t ee1004_eeprom_read(struct
 	if (offset + count > EE1004_PAGE_SIZE)
 		count = EE1004_PAGE_SIZE - offset;

+	if (count > I2C_SMBUS_BLOCK_MAX)
+		count = I2C_SMBUS_BLOCK_MAX;
+
 	return i2c_smbus_read_i2c_block_data_or_emulated(client, offset, count, buf);
 }