CVE-2026-45903

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

bpf: Fix memory access flags in helper prototypes

After commit 37cce22dbd51 (bpf: verifier: Refactor helper access type tracking), the verifier started relying on the access type flags in helper function prototypes to perform memory access optimizations.

Currently, several helper functions utilizing ARG_PTR_TO_MEM lack the corresponding MEM_RDONLY or MEM_WRITE flags. This omission causes the verifier to incorrectly assume that the buffer contents are unchanged across the helper call. Consequently, the verifier may optimize away subsequent reads based on this wrong assumption, leading to correctness issues.

For bpf_get_stack_proto_raw_tp, the original MEM_RDONLY was incorrect since the helper writes to the buffer. Change it to ARG_PTR_TO_UNINIT_MEM which correctly indicates write access to potentially uninitialized memory.

Similar issues were recently addressed for specific helpers in commit ac44dcc788b9 (bpf: Fix verifier assumptions of bpf_d_paths output buffer) and commit 2eb7648558a7 (bpf: Specify access type of bpf_sysctl_get_name args).

Fix these prototypes by adding the correct memory access flags.

Weakness

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

Affected Software

Potential Mitigations

• 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.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/802eef5afb1865bc5536a5302c068ba2215a1f72
• https://git.kernel.org/stable/c/aa319592892068bd960c1a1c07bd621085b0c63d
• https://git.kernel.org/stable/c/fdfe75161f6e8c41a7d3023fbb815b537107b806