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/alpha/boot/head.S | 124 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 arch/alpha/boot/head.S (limited to 'arch/alpha/boot/head.S') diff --git a/arch/alpha/boot/head.S b/arch/alpha/boot/head.S new file mode 100644 index 000000000..06a7c95fe --- /dev/null +++ b/arch/alpha/boot/head.S @@ -0,0 +1,124 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/boot/head.S + * + * initial bootloader stuff.. + */ + +#include + + .set noreorder + .globl __start + .ent __start +__start: + br $29,2f +2: ldgp $29,0($29) + jsr $26,start_kernel + call_pal PAL_halt + .end __start + + .align 5 + .globl wrent + .ent wrent +wrent: + .prologue 0 + call_pal PAL_wrent + ret ($26) + .end wrent + + .align 5 + .globl wrkgp + .ent wrkgp +wrkgp: + .prologue 0 + call_pal PAL_wrkgp + ret ($26) + .end wrkgp + + .align 5 + .globl switch_to_osf_pal + .ent switch_to_osf_pal +switch_to_osf_pal: + subq $30,128,$30 + .frame $30,128,$26 + stq $26,0($30) + stq $1,8($30) + stq $2,16($30) + stq $3,24($30) + stq $4,32($30) + stq $5,40($30) + stq $6,48($30) + stq $7,56($30) + stq $8,64($30) + stq $9,72($30) + stq $10,80($30) + stq $11,88($30) + stq $12,96($30) + stq $13,104($30) + stq $14,112($30) + stq $15,120($30) + .prologue 0 + + stq $30,0($17) /* save KSP in PCB */ + + bis $30,$30,$20 /* a4 = KSP */ + br $17,1f + + ldq $26,0($30) + ldq $1,8($30) + ldq $2,16($30) + ldq $3,24($30) + ldq $4,32($30) + ldq $5,40($30) + ldq $6,48($30) + ldq $7,56($30) + ldq $8,64($30) + ldq $9,72($30) + ldq $10,80($30) + ldq $11,88($30) + ldq $12,96($30) + ldq $13,104($30) + ldq $14,112($30) + ldq $15,120($30) + addq $30,128,$30 + ret ($26) +1: call_pal PAL_swppal + .end switch_to_osf_pal + + .align 3 + .globl tbi + .ent tbi +tbi: + .prologue 0 + call_pal PAL_tbi + ret ($26) + .end tbi + + .align 3 + .globl halt + .ent halt +halt: + .prologue 0 + call_pal PAL_halt + .end halt + +/* $16 - new stack page */ + .align 3 + .globl move_stack + .ent move_stack +move_stack: + .prologue 0 + lda $0, 0x1fff($31) + and $0, $30, $1 /* Stack offset */ + or $1, $16, $16 /* New stack pointer */ + mov $30, $1 + mov $16, $2 +1: ldq $3, 0($1) /* Move the stack */ + addq $1, 8, $1 + stq $3, 0($2) + and $0, $1, $4 + addq $2, 8, $2 + bne $4, 1b + mov $16, $30 + ret ($26) + .end move_stack -- cgit v1.3.1