CVE-2023-52775

In the Linux kernel, the following vulnerability has been resolved:

net/smc: avoid data corruption caused by decline

We found a data corruption issue during testing of SMC-R on Redis applications.

The benchmark has a low probability of reporting a strange error as shown below.

Error: Protocol error, got xe2 as reply type byte

Finally, we found that the retrieved error data was as follows:

0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C 0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2

It is quite obvious that this is a SMC DECLINE message, which means that the applications received SMC protocol message. We found that this was caused by the following situations:

client server ¦ clc proposal ————-> ¦ clc accept <————- ¦ clc confirm ————-> wait llc confirm send llc confirm ¦failed llc confirm ¦ x—— (after 2s)timeout wait llc confirm rsp

wait decline

(after 1s) timeout (after 2s) timeout ¦ decline ————–> ¦ decline <————–

As a result, a decline message was sent in the implementation, and this message was read from TCP by the already-fallback connection.

This patch double the client timeout as 2x of the server value, With this simple change, the Decline messages should never cross or collide (during Confirm link timeout).

This issue requires an immediate solution, since the protocol updates involve a more long-term solution.

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/5ada292b5c504720a0acef8cae9acc62a694d19c
• https://git.kernel.org/stable/c/7234d2b5dffa5af77fd4e0deaebab509e130c6b1
• https://git.kernel.org/stable/c/90072af9efe8c7bd7d086709014ddd44cebd5e7c
• https://git.kernel.org/stable/c/94a0ae698b4d5d5bb598e23228002a1491c50add
• https://git.kernel.org/stable/c/e6d71b437abc2f249e3b6a1ae1a7228e09c6e563
• https://git.kernel.org/stable/c/5ada292b5c504720a0acef8cae9acc62a694d19c
• https://git.kernel.org/stable/c/7234d2b5dffa5af77fd4e0deaebab509e130c6b1
• https://git.kernel.org/stable/c/90072af9efe8c7bd7d086709014ddd44cebd5e7c
• https://git.kernel.org/stable/c/94a0ae698b4d5d5bb598e23228002a1491c50add
• https://git.kernel.org/stable/c/e6d71b437abc2f249e3b6a1ae1a7228e09c6e563