From: Alexei Starovoitov Date: Thu, 2 Apr 2026 16:29:49 +0000 (-0700) Subject: Merge branch 'bpf-fix-abuse-of-kprobe_write_ctx-via-freplace' X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7601044020ac1c55675ee59422ef75b25a31bed;p=thirdparty%2Flinux.git Merge branch 'bpf-fix-abuse-of-kprobe_write_ctx-via-freplace' Leon Hwang says: ==================== bpf: Fix abuse of kprobe_write_ctx via freplace The potential issue of kprobe_write_ctx+freplace was mentioned in "bpf: Disallow !kprobe_write_ctx progs tail-calling kprobe_write_ctx progs" [1]. It is true issue, that the test in patch #2 verifies that kprobe_write_ctx=false kprobe progs can be abused to modify struct pt_regs via kprobe_write_ctx=true freplace progs. When struct pt_regs is modified, bpf_prog_test_run_opts() gets -EFAULT instead of 0. test_freplace_kprobe_write_ctx:FAIL:bpf_prog_test_run_opts unexpected error: -14 (errno 14) We will disallow attaching freplace programs on kprobe programs with different kprobe_write_ctx values. Links: [1] https://lore.kernel.org/bpf/CAP01T74w4KVMn9bEwpQXrk+bqcUxzb6VW1SQ_QvNy0A4EY-9Jg@mail.gmail.com/ Changes: v2 -> v3: * Add comment to the rejection of kprobe_write_ctx (per Jiri). * Use libbpf_get_error() instead of errno in test (per Jiri). * Collect Acked-by tags from Jiri and Song, thanks. v2: https://lore.kernel.org/bpf/20260326141718.17731-1-leon.hwang@linux.dev/ v1 -> v2: * Drop patch #1 in v1, as it wasn't an issue (per Toke). * Check kprobe_write_ctx value at attach time instead of at load time, to prevent attaching kprobe_write_ctx=true freplace progs on kprobe_write_ctx=false kprobe progs (per Gemini/sashiko). * Move kprobe_write_ctx test code to attach_probe.c and kprobe_write_ctx.c. v1: https://lore.kernel.org/bpf/20260324150444.68166-1-leon.hwang@linux.dev/ ==================== Link: https://patch.msgid.link/20260331145353.87606-1-leon.hwang@linux.dev Signed-off-by: Alexei Starovoitov --- f7601044020ac1c55675ee59422ef75b25a31bed