CVE-2023-53024CVE-2023-53024

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix pointer-leak due to insufficient speculative store bypass mitigation To mitigate Spectre v4, 2039f26f3aca ("bpf: Fix leakage due to insufficient speculative store bypass mitigation") inserts lfence instructions after 1) initializing a stack slot and 2) spilling a pointer to the stack. However, this does not cover cases where a stack slot is first initialized with a pointer (subject to sanitization) but then overwritten with a scalar (not subject to sanitization because the slot was already initialized). In this case, the second write may be subject to speculative store bypass (SSB) creating a speculative pointer-as-scalar type confusion. This allows the program to subsequently leak the numerical pointer value using, for example, a branch-based cache side channel. To fix this, also sanitize scalars if they write a stack slot that previously contained a pointer. Assuming that pointer-spills are only generate