From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/arm/lib/csumpartialcopyuser.S | 101 +++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 arch/arm/lib/csumpartialcopyuser.S (limited to 'arch/arm/lib/csumpartialcopyuser.S') diff --git a/arch/arm/lib/csumpartialcopyuser.S b/arch/arm/lib/csumpartialcopyuser.S new file mode 100644 index 000000000..c289bde04 --- /dev/null +++ b/arch/arm/lib/csumpartialcopyuser.S @@ -0,0 +1,101 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/csumpartialcopyuser.S + * + * Copyright (C) 1995-1998 Russell King + * + * 27/03/03 Ian Molton Clean up CONFIG_CPU + */ +#include +#include +#include +#include + + .text + +#if defined(CONFIG_CPU_SW_DOMAIN_PAN) + + .macro save_regs + mrc p15, 0, ip, c3, c0, 0 + stmfd sp!, {r1, r2, r4 - r8, ip, lr} + uaccess_enable ip + .endm + + .macro load_regs + ldmfd sp!, {r1, r2, r4 - r8, ip, lr} + mcr p15, 0, ip, c3, c0, 0 + ret lr + .endm + +#elif defined(CONFIG_CPU_TTBR0_PAN) + + .macro save_regs + mrc p15, 0, ip, c2, c0, 2 @ read TTBCR + stmfd sp!, {r1, r2, r4 - r8, ip, lr} + uaccess_enable ip + .endm + + .macro load_regs + ldmfd sp!, {r1, r2, r4 - r8, ip, lr} + mcr p15, 0, ip, c2, c0, 2 @ restore TTBCR + ret lr + .endm + +#else + + .macro save_regs + stmfd sp!, {r1, r2, r4 - r8, lr} + .endm + + .macro load_regs + ldmfd sp!, {r1, r2, r4 - r8, pc} + .endm + +#endif + + .macro load1b, reg1 + ldrusr \reg1, r0, 1 + .endm + + .macro load2b, reg1, reg2 + ldrusr \reg1, r0, 1 + ldrusr \reg2, r0, 1 + .endm + + .macro load1l, reg1 + ldrusr \reg1, r0, 4 + .endm + + .macro load2l, reg1, reg2 + ldrusr \reg1, r0, 4 + ldrusr \reg2, r0, 4 + .endm + + .macro load4l, reg1, reg2, reg3, reg4 + ldrusr \reg1, r0, 4 + ldrusr \reg2, r0, 4 + ldrusr \reg3, r0, 4 + ldrusr \reg4, r0, 4 + .endm + +/* + * unsigned int + * csum_partial_copy_from_user(const char *src, char *dst, int len) + * r0 = src, r1 = dst, r2 = len + * Returns : r0 = checksum or 0 + */ + +#define FN_ENTRY ENTRY(csum_partial_copy_from_user) +#define FN_EXIT ENDPROC(csum_partial_copy_from_user) + +#include "csumpartialcopygeneric.S" + +/* + * We report fault by returning 0 csum - impossible in normal case, since + * we start with 0xffffffff for initial sum. + */ + .pushsection .text.fixup,"ax" + .align 4 +9001: mov r0, #0 + load_regs + .popsection -- cgit v1.3.1