selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 148 insertions, 0 deletions

diff --git a/arch/arm/mm/cache-v4.S b/arch/arm/mm/cache-v4.S
new file mode 100644
index 000000000..001d7042b
--- /dev/null
+++ b/arch/arm/mm/cache-v4.S
@@ -0,0 +1,148 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/arch/arm/mm/cache-v4.S
+ *
+ *  Copyright (C) 1997-2002 Russell king
+ */
+#include <linux/linkage.h>
+#include <linux/init.h>
+#include <linux/cfi_types.h>
+#include <asm/assembler.h>
+#include <asm/page.h>
+#include "proc-macros.S"
+
+/*
+ *	flush_icache_all()
+ *
+ *	Unconditionally clean and invalidate the entire icache.
+ */
+SYM_TYPED_FUNC_START(v4_flush_icache_all)
+	ret	lr
+SYM_FUNC_END(v4_flush_icache_all)
+
+/*
+ *	flush_user_cache_all()
+ *
+ *	Invalidate all cache entries in a particular address
+ *	space.
+ *
+ *	- mm	- mm_struct describing address space
+ */
+SYM_FUNC_ALIAS(v4_flush_user_cache_all, v4_flush_kern_cache_all)
+
+/*
+ *	flush_kern_cache_all()
+ *
+ *	Clean and invalidate the entire cache.
+ */
+SYM_TYPED_FUNC_START(v4_flush_kern_cache_all)
+#ifdef CONFIG_CPU_CP15
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c7, 0		@ flush ID cache
+	ret	lr
+#else
+	ret	lr
+#endif
+SYM_FUNC_END(v4_flush_kern_cache_all)
+
+/*
+ *	flush_user_cache_range(start, end, flags)
+ *
+ *	Invalidate a range of cache entries in the specified
+ *	address space.
+ *
+ *	- start - start address (may not be aligned)
+ *	- end	- end address (exclusive, may not be aligned)
+ *	- flags	- vma_area_struct flags describing address space
+ */
+SYM_TYPED_FUNC_START(v4_flush_user_cache_range)
+#ifdef CONFIG_CPU_CP15
+	mov	ip, #0
+	mcr	p15, 0, ip, c7, c7, 0		@ flush ID cache
+	ret	lr
+#else
+	ret	lr
+#endif
+SYM_FUNC_END(v4_flush_user_cache_range)
+
+/*
+ *	coherent_kern_range(start, end)
+ *
+ *	Ensure coherency between the Icache and the Dcache in the
+ *	region described by start.  If you have non-snooping
+ *	Harvard caches, you need to implement this function.
+ *
+ *	- start  - virtual start address
+ *	- end	 - virtual end address
+ */
+SYM_TYPED_FUNC_START(v4_coherent_kern_range)
+	ret	lr
+SYM_FUNC_END(v4_coherent_kern_range)
+
+/*
+ *	coherent_user_range(start, end)
+ *
+ *	Ensure coherency between the Icache and the Dcache in the
+ *	region described by start.  If you have non-snooping
+ *	Harvard caches, you need to implement this function.
+ *
+ *	- start  - virtual start address
+ *	- end	 - virtual end address
+ */
+SYM_TYPED_FUNC_START(v4_coherent_user_range)
+	mov	r0, #0
+	ret	lr
+SYM_FUNC_END(v4_coherent_user_range)
+
+/*
+ *	flush_kern_dcache_area(void *addr, size_t size)
+ *
+ *	Ensure no D cache aliasing occurs, either with itself or
+ *	the I cache
+ *
+ *	- addr	- kernel address
+ *	- size	- region size
+ */
+SYM_TYPED_FUNC_START(v4_flush_kern_dcache_area)
+#ifdef CONFIG_CFI /* Fallthrough if !CFI */
+	b	v4_dma_flush_range
+#endif
+SYM_FUNC_END(v4_flush_kern_dcache_area)
+
+/*
+ *	dma_flush_range(start, end)
+ *
+ *	Clean and invalidate the specified virtual address range.
+ *
+ *	- start  - virtual start address
+ *	- end	 - virtual end address
+ */
+SYM_TYPED_FUNC_START(v4_dma_flush_range)
+#ifdef CONFIG_CPU_CP15
+	mov	r0, #0
+	mcr	p15, 0, r0, c7, c7, 0		@ flush ID cache
+#endif
+	ret	lr
+SYM_FUNC_END(v4_dma_flush_range)
+
+/*
+ *	dma_unmap_area(start, size, dir)
+ *	- start	- kernel virtual start address
+ *	- size	- size of region
+ *	- dir	- DMA direction
+ */
+SYM_TYPED_FUNC_START(v4_dma_unmap_area)
+	teq	r2, #DMA_TO_DEVICE
+	bne	v4_dma_flush_range
+	ret	lr
+SYM_FUNC_END(v4_dma_unmap_area)
+
+/*
+ *	dma_map_area(start, size, dir)
+ *	- start	- kernel virtual start address
+ *	- size	- size of region
+ *	- dir	- DMA direction
+ */
+SYM_TYPED_FUNC_START(v4_dma_map_area)
+	ret	lr
+SYM_FUNC_END(v4_dma_map_area)