A vulnerability in the media/dvb-frontends/dib300mb module of the Linux kernel has been fixed. The issue pertains to an uninitialized value when using the dib300_write_reg function. The vulnerability was reported by Syzbot [1] using the KMSAN tool. In this post, we will explore the nature of the bug, how the fix was implemented, and how to verify the new changes.
Exploit Details
The bug occurred in the dib300_read_reg() function - local u8 rb[2] is used in i2c_transfer() as a read buffer. However, in case the i2c_transfer() call fails, the buffer may end up with undefined values. This could have potential downstream negative effects for the associated subsystems, especially if the uninitialized values are used in further operations, potentially leading to undefined behaviors.
Solution Overview
The proposed fix is to simply zero out the rb buffer so that no undefined values are left in it. This is achieved by using the memset function in C to zero out the buffer. It can be done as shown in the following code snippet:
Verification
This change has been reported to have resolved the issue with regards to the uninitialized values in dib300_read_reg(). You can update to the new kernel version to ensure your system is protected against this vulnerability.
References
[1] Syzkaller report - https://url-to-the-syzkaller-report
[2] Full patch - https://url-to-the-full-patch
Conclusion
The patch that resolves the uninitialized value issue in dib300_write_reg function within the Linux kernel's media/dvb-frontends/dib300mb module is a step in the right direction for maintaining optimal security and functionality. It is recommended that developers and users alike update their kernel versions to include this patch. The Linux kernel development community continues to show commitment to addressing vulnerabilities, and this fix is another example of that determination.
Timeline
Published on: 01/06/2025 17:15:44 UTC
Last modified on: 01/07/2025 22:49:54 UTC