i2c: rtl9300: ensure data length is within supported range
Add an explicit check for the xfer length to 'rtl9300_i2c_config_xfer'
to ensure the data length isn't within the supported range. In
particular a data length of 0 is not supported by the hardware and
causes unintended or destructive behaviour.
This limitation becomes obvious when looking at the register
documentation [1]. 4 bits are reserved for DATA_WIDTH and the value
of these 4 bits is used as N + 1, allowing a data length range of
1 <= len <= 16.
Affected by this is the SMBus Quick Operation which works with a data
length of 0. Passing 0 as the length causes an underflow of the value
due to:
(len - 1) & 0xf
and effectively specifying a transfer length of 16 via the registers.
This causes a 16-byte write operation instead of a Quick Write. For
example, on SFP modules without write-protected EEPROM this soft-bricks
them by overwriting some initial bytes.
For completeness, also add a quirk for the zero length.
[1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2
Tracking
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Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
Wed, 14 Jan 2026 18:15:00 +0000
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| Metrics |
ssvc
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Wed, 10 Dec 2025 22:00:00 +0000
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| Weaknesses | CWE-191 | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:* |
Fri, 03 Oct 2025 00:15:00 +0000
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| Metrics |
threat_severity
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cvssV3_1
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Thu, 02 Oct 2025 09:00:00 +0000
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| First Time appeared |
Linux
Linux linux Kernel |
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| Vendors & Products |
Linux
Linux linux Kernel |
Wed, 01 Oct 2025 08:15:00 +0000
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| Description | In the Linux kernel, the following vulnerability has been resolved: i2c: rtl9300: ensure data length is within supported range Add an explicit check for the xfer length to 'rtl9300_i2c_config_xfer' to ensure the data length isn't within the supported range. In particular a data length of 0 is not supported by the hardware and causes unintended or destructive behaviour. This limitation becomes obvious when looking at the register documentation [1]. 4 bits are reserved for DATA_WIDTH and the value of these 4 bits is used as N + 1, allowing a data length range of 1 <= len <= 16. Affected by this is the SMBus Quick Operation which works with a data length of 0. Passing 0 as the length causes an underflow of the value due to: (len - 1) & 0xf and effectively specifying a transfer length of 16 via the registers. This causes a 16-byte write operation instead of a Quick Write. For example, on SFP modules without write-protected EEPROM this soft-bricks them by overwriting some initial bytes. For completeness, also add a quirk for the zero length. [1] https://svanheule.net/realtek/longan/register/i2c_mst1_ctrl2 | |
| Title | i2c: rtl9300: ensure data length is within supported range | |
| References |
|
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-01-14T17:42:45.737Z
Reserved: 2025-04-16T07:20:57.147Z
Link: CVE-2025-39928
Updated: 2026-01-14T17:39:19.625Z
Status : Modified
Published: 2025-10-01T08:15:36.230
Modified: 2026-01-14T18:16:41.390
Link: CVE-2025-39928
OpenCVE Enrichment
Updated: 2025-10-02T08:40:14Z