CVE-2024-42148

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

bnx2x: Fix multiple UBSAN array-index-out-of-bounds

Fix UBSAN warnings that occur when using a system with 32 physical cpu cores or more, or when the user defines a number of Ethernet queues greater than or equal to FP_SB_MAX_E1x using the num_queues module parameter.

Currently there is a read/write out of bounds that occurs on the array struct stats_query_entry query present inside the bnx2x_fw_stats_req struct in drivers/net/ethernet/broadcom/bnx2x/bnx2x.h. Looking at the definition of the struct stats_query_entry query array:

struct stats_query_entry query[FP_SB_MAX_E1x+ BNX2X_FIRST_QUEUE_QUERY_IDX];

FP_SB_MAX_E1x is defined as the maximum number of fast path interrupts and has a value of 16, while BNX2X_FIRST_QUEUE_QUERY_IDX has a value of 3 meaning the array has a total size of 19. Since accesses to struct stats_query_entry query are offset-ted by BNX2X_FIRST_QUEUE_QUERY_IDX, that means that the total number of Ethernet queues should not exceed FP_SB_MAX_E1x (16). However one of these queues is reserved for FCOE and thus the number of Ethernet queues should be set to [FP_SB_MAX_E1x -1] (15) if FCOE is enabled or [FP_SB_MAX_E1x] (16) if it is not.

This is also described in a comment in the source code in drivers/net/ethernet/broadcom/bnx2x/bnx2x.h just above the Macro definition of FP_SB_MAX_E1x. Below is the part of this explanation that it important for this patch

/*

• The total number of L2 queues, MSIX vectors and HW contexts (CIDs) is
• control by the number of fast-path status blocks supported by the
• device (HW/FW). Each fast-path status block (FP-SB) aka non-default
• status block represents an independent interrupts context that can
• serve a regular L2 networking queue. However special L2 queues such
• as the FCoE queue do not require a FP-SB and other components like
• the CNIC may consume FP-SB reducing the number of possible L2 queues
• If the maximum number of FP-SB available is X then:
• a. If CNIC is supported it consumes 1 FP-SB thus the max number of
• regular L2 queues is Y=X-1
• b. In MF mode the actual number of L2 queues is Y= (X-1/MF_factor)
• c. If the FCoE L2 queue is supported the actual number of L2 queues
• is Y+1
• d. The number of irqs (MSIX vectors) is either Y+1 (one extra for
• slow-path interrupts) or Y+2 if CNIC is supported (one additional
• FP interrupt context for the CNIC).
• e. The number of HW context (CID count) is always X or X+1 if FCoE
• L2 queue is supported. The cid for the FCoE L2 queue is always X. */

However this driver also supports NICs that use the E2 controller which can handle more queues due to having more FP-SB represented by FP_SB_MAX_E2. Looking at the commits when the E2 support was added, it was originally using the E1x parameters: commit f2e0899f0f27 (bnx2x: Add 57712 support). Back then FP_SB_MAX_E2 was set to 16 the same as E1x. However the driver was later updated to take full advantage of the E2 instead of having it be limited to the capabilities of the E1x. But as far as we can tell, the array stats_query_entry query was still limited to using the FP-SB available to the E1x cards as part of an oversignt when the driver was updated to take full advantage of the E2, and now with the driver being aware of the greater queue size supported by E2 NICs, it causes the UBSAN warnings seen in the stack traces below.

This patch increases the size of the stats_query_entry query array by replacing FP_SB_MAX_E1x with FP_SB_MAX_E2 to be large enough to handle both types of NICs.

Stack traces:

UBSAN: array-index-out-of-bounds in drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c:1529:11 index 20 is out of range for type stats_query_entry [19] CPU: 12 PID: 858 Comm: systemd-network Not tainted 6.9.0-060900rc7-generic #202405052133 Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 —truncated—

Weakness

The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.

Affected Software

Potential Mitigations

• For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
• Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, Ada allows the programmer to constrain the values of a variable and languages such as Java and Ruby will allow the programmer to handle exceptions when an out-of-bounds index is accessed.
• 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].
• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• When accessing a user-controlled array index, use a stringent range of values that are within the target array. Make sure that you do not allow negative values to be used. That is, verify the minimum as well as the maximum of the range of acceptable values.
• Run the code in a “jail” or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
• OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
• This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
• Be careful to avoid CWE-243 and other weaknesses related to jails.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/100.html

References

• https://git.kernel.org/stable/c/0edae06b4c227bcfaf3ce21208d49191e1009d3b
• https://git.kernel.org/stable/c/134061163ee5ca4759de5c24ca3bd71608891ba7
• https://git.kernel.org/stable/c/8b17cec33892a66bbd71f8d9a70a45e2072ae84f
• https://git.kernel.org/stable/c/9504a1550686f53b0bab4cab31d435383b1ee2ce
• https://git.kernel.org/stable/c/b9ea38e767459111a511ed4fb74abc37db95a59d
• https://git.kernel.org/stable/c/cbe53087026ad929cd3950508397e8892a6a2a0f
• https://git.kernel.org/stable/c/cfb04472ce33bee2579caf4dc9f4242522f6e26e
• https://git.kernel.org/stable/c/f1313ea92f82451923e28ab45a4aaa0e70e80b98