bpf: fix constant blinding bypass for PROBE_MEM32 stores#11340
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bpf: fix constant blinding bypass for PROBE_MEM32 stores#11340kernel-patches-daemon-bpf[bot] wants to merge 2 commits intobpf_basefrom
kernel-patches-daemon-bpf[bot] wants to merge 2 commits intobpf_basefrom
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BPF_ST | BPF_PROBE_MEM32 immediate stores are not handled by bpf_jit_blind_insn(), allowing user-controlled 32-bit immediates to survive unblinded into JIT-compiled native code when bpf_jit_harden >= 1. The root cause is that convert_ctx_accesses() rewrites BPF_ST|BPF_MEM to BPF_ST|BPF_PROBE_MEM32 for arena pointer stores during verification, before bpf_jit_blind_constants() runs during JIT compilation. The blinding switch only matches BPF_ST|BPF_MEM (mode 0x60), not BPF_ST|BPF_PROBE_MEM32 (mode 0xa0). The instruction falls through unblinded. Add BPF_ST|BPF_PROBE_MEM32 cases to bpf_jit_blind_insn() alongside the existing BPF_ST|BPF_MEM cases. The blinding transformation is identical: load the blinded immediate into BPF_REG_AX via mov+xor, then convert the immediate store to a register store (BPF_STX). The rewritten STX instruction must preserve the BPF_PROBE_MEM32 mode so the architecture JIT emits the correct arena addressing (R12-based on x86-64). Cannot use the BPF_STX_MEM() macro here because it hardcodes BPF_MEM mode; construct the instruction directly instead. Fixes: 6082b6c ("bpf: Recognize addr_space_cast instruction in the verifier.") Reviewed-by: Puranjay Mohan <puranjay@kernel.org> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Sachin Kumar <xcyfun@protonmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=1063861 irrelevant now. Closing PR. |
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Pull request for series with
subject: bpf: fix constant blinding bypass for PROBE_MEM32 stores
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1063861