[PATCH AUTOSEL 6.6 13/62] i2c: tegra: check msg length in SMBUS block read

[Sasha Levin <sashal@kernel.org>]

From: Akhil R <akhilrajeev@nvidia.com>

[ Upstream commit a6e04f05ce0b070ab39d5775580e65c7d943da0b ]

For SMBUS block read, do not continue to read if the message length
passed from the device is '0' or greater than the maximum allowed bytes.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20250424053320.19211-1-akhilrajeev@nvidia.com
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

Based on my analysis of both the commit message, code changes, and the
kernel tree context, here is my assessment: **YES** This commit should
be backported to stable kernel trees for the following reasons: ##
Analysis of Code Changes The commit adds a critical validation check for
SMBUS block read operations: ```c /bin /bin.usr-is-merged /boot /dev
/etc /home /init /lib /lib.usr-is-merged /lib64 /lost+found /media /mnt
/opt /proc /root /run /sbin /sbin.usr-is-merged /snap /srv /sys /tmp
/usr /var Validate message length before proceeding linux/ if
(msgs[i].buf[0] == 0 || msgs[i].buf[0] > I2C_SMBUS_BLOCK_MAX) break; ```
## Why This Should Be Backported: ### 1. **Security and Data Integrity
Protection** The change prevents two critical issues: - **Buffer
overflow protection**: Without this check, a malicious or faulty device
could specify a block length > 32 bytes (I2C_SMBUS_BLOCK_MAX), causing
the driver to read beyond allocated buffer boundaries - **Zero-length
validation**: Prevents processing zero-length blocks which could cause
undefined behavior in subsequent operations ### 2. **Clear Bug Fix
Nature** This is a straightforward bug fix that: - Adds missing input
validation for a critical path - Uses existing constants
(I2C_SMBUS_BLOCK_MAX = 32) - Follows validation patterns used in other
I2C drivers - Is confined to a single, well-understood code path ### 3.
**Minimal Risk and Contained Change** - Only 3 lines of code added -
Simple conditional check with well-defined behavior - No architectural
changes or new features - Limited to SMBUS block read functionality in
Tegra I2C driver ### 4. **Alignment with Stable Tree Criteria**
Examining the similar commits provided: - **Similar Commit #2** (YES
status): Also a bug fix for SMBUS block read functionality - **Similar
Commit #4** (YES status): Simple validation improvement using core
functionality - Both demonstrate that contained I2C validation fixes are
appropriate for backporting ### 5. **Critical Subsystem Protection** I2C
is a fundamental communication protocol used throughout embedded
systems. SMBUS block reads are commonly used for: - Battery management
systems - Temperature sensors - EEPROM access - Hardware monitoring
Unvalidated block lengths could lead to system instability or security
vulnerabilities. ### 6. **Follows Precedent** The commit references
fixing behavior "for SMBUS block read" - this type of protocol-specific
validation fix has been consistently backported in similar scenarios. ##
Risk Assessment: **LOW** - Simple validation addition - Well-tested I2C
constant (I2C_SMBUS_BLOCK_MAX) - Fail-safe behavior (breaks loop on
invalid input) - No impact on valid use cases This commit represents
exactly the type of important, low-risk bug fix that stable trees are
designed to include.

 drivers/i2c/busses/i2c-tegra.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 91be04b534fe6..08a81daedc115 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1397,6 +1397,11 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], MSG_END_CONTINUE);
 			if (ret)
 				break;
+
+			/* Validate message length before proceeding */
+			if (msgs[i].buf[0] == 0 || msgs[i].buf[0] > I2C_SMBUS_BLOCK_MAX)
+				break;
+
 			/* Set the msg length from first byte */
 			msgs[i].len += msgs[i].buf[0];
 			dev_dbg(i2c_dev->dev, "reading %d bytes\n", msgs[i].len);
-- 
2.39.5