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/putuser.S | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 arch/arm/lib/putuser.S (limited to 'arch/arm/lib/putuser.S') diff --git a/arch/arm/lib/putuser.S b/arch/arm/lib/putuser.S new file mode 100644 index 000000000..bdd8836dc --- /dev/null +++ b/arch/arm/lib/putuser.S @@ -0,0 +1,95 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/putuser.S + * + * Copyright (C) 2001 Russell King + * + * Idea from x86 version, (C) Copyright 1998 Linus Torvalds + * + * These functions have a non-standard call interface to make + * them more efficient, especially as they return an error + * value in addition to the "real" return value. + * + * __put_user_X + * + * Inputs: r0 contains the address + * r1 contains the address limit, which must be preserved + * r2, r3 contains the value + * Outputs: r0 is the error code + * lr corrupted + * + * No other registers must be altered. (see + * for specific ASM register usage). + * + * Note that ADDR_LIMIT is either 0 or 0xc0000000 + * Note also that it is intended that __put_user_bad is not global. + */ +#include +#include +#include +#include + +ENTRY(__put_user_1) + check_uaccess r0, 1, r1, ip, __put_user_bad +1: TUSER(strb) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__put_user_1) + +ENTRY(__put_user_2) + check_uaccess r0, 2, r1, ip, __put_user_bad +#if __LINUX_ARM_ARCH__ >= 6 + +2: TUSER(strh) r2, [r0] + +#else + + mov ip, r2, lsr #8 +#ifndef __ARMEB__ +2: TUSER(strb) r2, [r0], #1 +3: TUSER(strb) ip, [r0] +#else +2: TUSER(strb) ip, [r0], #1 +3: TUSER(strb) r2, [r0] +#endif + +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + mov r0, #0 + ret lr +ENDPROC(__put_user_2) + +ENTRY(__put_user_4) + check_uaccess r0, 4, r1, ip, __put_user_bad +4: TUSER(str) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__put_user_4) + +ENTRY(__put_user_8) + check_uaccess r0, 8, r1, ip, __put_user_bad +#ifdef CONFIG_THUMB2_KERNEL +5: TUSER(str) r2, [r0] +6: TUSER(str) r3, [r0, #4] +#else +5: TUSER(str) r2, [r0], #4 +6: TUSER(str) r3, [r0] +#endif + mov r0, #0 + ret lr +ENDPROC(__put_user_8) + +__put_user_bad: + mov r0, #-EFAULT + ret lr +ENDPROC(__put_user_bad) + +.pushsection __ex_table, "a" + .long 1b, __put_user_bad + .long 2b, __put_user_bad +#if __LINUX_ARM_ARCH__ < 6 + .long 3b, __put_user_bad +#endif + .long 4b, __put_user_bad + .long 5b, __put_user_bad + .long 6b, __put_user_bad +.popsection -- cgit v1.3.1