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/io-readsb.S | 120 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 arch/arm/lib/io-readsb.S (limited to 'arch/arm/lib/io-readsb.S') diff --git a/arch/arm/lib/io-readsb.S b/arch/arm/lib/io-readsb.S new file mode 100644 index 000000000..0def9388f --- /dev/null +++ b/arch/arm/lib/io-readsb.S @@ -0,0 +1,120 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/io-readsb.S + * + * Copyright (C) 1995-2000 Russell King + */ +#include +#include + +.Linsb_align: rsb ip, ip, #4 + cmp ip, r2 + movgt ip, r2 + cmp ip, #2 + ldrb r3, [r0] + strb r3, [r1], #1 + ldrbge r3, [r0] + strbge r3, [r1], #1 + ldrbgt r3, [r0] + strbgt r3, [r1], #1 + subs r2, r2, ip + bne .Linsb_aligned + +ENTRY(__raw_readsb) + teq r2, #0 @ do we have to check for the zero len? + reteq lr + ands ip, r1, #3 + bne .Linsb_align + +.Linsb_aligned: stmfd sp!, {r4 - r6, lr} + + subs r2, r2, #16 + bmi .Linsb_no_16 + +.Linsb_16_lp: ldrb r3, [r0] + ldrb r4, [r0] + ldrb r5, [r0] + mov r3, r3, put_byte_0 + ldrb r6, [r0] + orr r3, r3, r4, put_byte_1 + ldrb r4, [r0] + orr r3, r3, r5, put_byte_2 + ldrb r5, [r0] + orr r3, r3, r6, put_byte_3 + ldrb r6, [r0] + mov r4, r4, put_byte_0 + ldrb ip, [r0] + orr r4, r4, r5, put_byte_1 + ldrb r5, [r0] + orr r4, r4, r6, put_byte_2 + ldrb r6, [r0] + orr r4, r4, ip, put_byte_3 + ldrb ip, [r0] + mov r5, r5, put_byte_0 + ldrb lr, [r0] + orr r5, r5, r6, put_byte_1 + ldrb r6, [r0] + orr r5, r5, ip, put_byte_2 + ldrb ip, [r0] + orr r5, r5, lr, put_byte_3 + ldrb lr, [r0] + mov r6, r6, put_byte_0 + orr r6, r6, ip, put_byte_1 + ldrb ip, [r0] + orr r6, r6, lr, put_byte_2 + orr r6, r6, ip, put_byte_3 + stmia r1!, {r3 - r6} + + subs r2, r2, #16 + bpl .Linsb_16_lp + + tst r2, #15 + ldmfdeq sp!, {r4 - r6, pc} + +.Linsb_no_16: tst r2, #8 + beq .Linsb_no_8 + + ldrb r3, [r0] + ldrb r4, [r0] + ldrb r5, [r0] + mov r3, r3, put_byte_0 + ldrb r6, [r0] + orr r3, r3, r4, put_byte_1 + ldrb r4, [r0] + orr r3, r3, r5, put_byte_2 + ldrb r5, [r0] + orr r3, r3, r6, put_byte_3 + ldrb r6, [r0] + mov r4, r4, put_byte_0 + ldrb ip, [r0] + orr r4, r4, r5, put_byte_1 + orr r4, r4, r6, put_byte_2 + orr r4, r4, ip, put_byte_3 + stmia r1!, {r3, r4} + +.Linsb_no_8: tst r2, #4 + beq .Linsb_no_4 + + ldrb r3, [r0] + ldrb r4, [r0] + ldrb r5, [r0] + ldrb r6, [r0] + mov r3, r3, put_byte_0 + orr r3, r3, r4, put_byte_1 + orr r3, r3, r5, put_byte_2 + orr r3, r3, r6, put_byte_3 + str r3, [r1], #4 + +.Linsb_no_4: ands r2, r2, #3 + ldmfdeq sp!, {r4 - r6, pc} + + cmp r2, #2 + ldrb r3, [r0] + strb r3, [r1], #1 + ldrbge r3, [r0] + strbge r3, [r1], #1 + ldrbgt r3, [r0] + strbgt r3, [r1] + + ldmfd sp!, {r4 - r6, pc} +ENDPROC(__raw_readsb) -- cgit v1.3.1