i2c: stub: Reject I2C block transfers with invalid length

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64191
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-20 17:18:22 UTC
Updated2026-07-20 17:18:22 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter. A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer: BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: <TASK> stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) </TASK> The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not. Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 7e9072dbd5f2f17934751873450d2c22080ead80 git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 4bd8635f28c135a08aac6badcd7d9b5cdb34335f git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 5f4d2bd028ebb6e4c09a9d64842546022321d4a7 git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 0526931b16e5a118d367b7bfce7d797e63f7ac69 git Not specified
CNA Linux Linux affected 4710317891e4824ce1510a6b5066abbd3e917750 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e git Not specified
CNA Linux Linux affected 2.6.33 Not specified
CNA Linux Linux unaffected 2.6.33 semver Not specified
CNA Linux Linux unaffected 5.10.260 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.211 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.177 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.144 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.95 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.37 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.14 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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