CVE-2026-64191

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> i2c: stub: Reject I2C block transfers with invalid length<br /> <br /> The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data-&gt;block[0]<br /> as the transfer length. The existing check only clamps it to avoid<br /> overrunning the chip-&gt;words[256] register array, but does not validate<br /> it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union<br /> i2c_smbus_data.block buffer (34 bytes total). The driver is a<br /> development/test tool (CONFIG_I2C_STUB=m, not built by default)<br /> that must be loaded with a chip_addr= parameter.<br /> <br /> A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl<br /> with I2C_SMBUS_I2C_BLOCK_DATA and data-&gt;block[0] &gt; 32, causing<br /> stub_xfer() to read or write past the end of the union<br /> i2c_smbus_data.block buffer:<br /> <br /> BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223)<br /> Read of size 1 at addr ffff88800abcfd92 by task exploit/81<br /> Call Trace:<br /> <br /> stub_xfer (drivers/i2c/i2c-stub.c:223)<br /> __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593)<br /> i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536)<br /> i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391)<br /> i2cdev_ioctl (drivers/i2c/i2c-dev.c:478)<br /> __x64_sys_ioctl (fs/ioctl.c:583)<br /> do_syscall_64 (arch/x86/entry/syscall_64.c:94)<br /> entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)<br /> <br /> <br /> The bug exists because i2c-stub implements .smbus_xfer directly,<br /> bypassing the I2C_SMBUS_BLOCK_MAX validation in<br /> i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same<br /> function correctly validates against I2C_SMBUS_BLOCK_MAX, but the<br /> I2C_SMBUS_I2C_BLOCK_DATA case does not.<br /> <br /> Fix by rejecting transfers with data-&gt;block[0] == 0 or<br /> data-&gt;block[0] &gt; I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with<br /> both the I2C_SMBUS_BLOCK_DATA case in the same function and the<br /> I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().