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/csumpartial.S | 139 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 139 insertions(+) create mode 100644 arch/arm/lib/csumpartial.S (limited to 'arch/arm/lib/csumpartial.S') diff --git a/arch/arm/lib/csumpartial.S b/arch/arm/lib/csumpartial.S new file mode 100644 index 000000000..87c9471be --- /dev/null +++ b/arch/arm/lib/csumpartial.S @@ -0,0 +1,139 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/csumpartial.S + * + * Copyright (C) 1995-1998 Russell King + */ +#include +#include + + .text + +/* + * Function: __u32 csum_partial(const char *src, int len, __u32 sum) + * Params : r0 = buffer, r1 = len, r2 = checksum + * Returns : r0 = new checksum + */ + +buf .req r0 +len .req r1 +sum .req r2 +td0 .req r3 +td1 .req r4 @ save before use +td2 .req r5 @ save before use +td3 .req lr + +.Lzero: mov r0, sum + add sp, sp, #4 + ldr pc, [sp], #4 + + /* + * Handle 0 to 7 bytes, with any alignment of source and + * destination pointers. Note that when we get here, C = 0 + */ +.Lless8: teq len, #0 @ check for zero count + beq .Lzero + + /* we must have at least one byte. */ + tst buf, #1 @ odd address? + movne sum, sum, ror #8 + ldrbne td0, [buf], #1 + subne len, len, #1 + adcsne sum, sum, td0, put_byte_1 + +.Lless4: tst len, #6 + beq .Lless8_byte + + /* we are now half-word aligned */ + +.Lless8_wordlp: +#if __LINUX_ARM_ARCH__ >= 4 + ldrh td0, [buf], #2 + sub len, len, #2 +#else + ldrb td0, [buf], #1 + ldrb td3, [buf], #1 + sub len, len, #2 +#ifndef __ARMEB__ + orr td0, td0, td3, lsl #8 +#else + orr td0, td3, td0, lsl #8 +#endif +#endif + adcs sum, sum, td0 + tst len, #6 + bne .Lless8_wordlp + +.Lless8_byte: tst len, #1 @ odd number of bytes + ldrbne td0, [buf], #1 @ include last byte + adcsne sum, sum, td0, put_byte_0 @ update checksum + +.Ldone: adc r0, sum, #0 @ collect up the last carry + ldr td0, [sp], #4 + tst td0, #1 @ check buffer alignment + movne r0, r0, ror #8 @ rotate checksum by 8 bits + ldr pc, [sp], #4 @ return + +.Lnot_aligned: tst buf, #1 @ odd address + ldrbne td0, [buf], #1 @ make even + subne len, len, #1 + adcsne sum, sum, td0, put_byte_1 @ update checksum + + tst buf, #2 @ 32-bit aligned? +#if __LINUX_ARM_ARCH__ >= 4 + ldrhne td0, [buf], #2 @ make 32-bit aligned + subne len, len, #2 +#else + ldrbne td0, [buf], #1 + ldrbne ip, [buf], #1 + subne len, len, #2 +#ifndef __ARMEB__ + orrne td0, td0, ip, lsl #8 +#else + orrne td0, ip, td0, lsl #8 +#endif +#endif + adcsne sum, sum, td0 @ update checksum + ret lr + +ENTRY(csum_partial) + stmfd sp!, {buf, lr} + cmp len, #8 @ Ensure that we have at least + blo .Lless8 @ 8 bytes to copy. + + tst buf, #1 + movne sum, sum, ror #8 + + adds sum, sum, #0 @ C = 0 + tst buf, #3 @ Test destination alignment + blne .Lnot_aligned @ align destination, return here + +1: bics ip, len, #31 + beq 3f + + stmfd sp!, {r4 - r5} +2: ldmia buf!, {td0, td1, td2, td3} + adcs sum, sum, td0 + adcs sum, sum, td1 + adcs sum, sum, td2 + adcs sum, sum, td3 + ldmia buf!, {td0, td1, td2, td3} + adcs sum, sum, td0 + adcs sum, sum, td1 + adcs sum, sum, td2 + adcs sum, sum, td3 + sub ip, ip, #32 + teq ip, #0 + bne 2b + ldmfd sp!, {r4 - r5} + +3: tst len, #0x1c @ should not change C + beq .Lless4 + +4: ldr td0, [buf], #4 + sub len, len, #4 + adcs sum, sum, td0 + tst len, #0x1c + bne 4b + b .Lless4 +ENDPROC(csum_partial) -- cgit v1.3.1