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, 61 insertions, 0 deletions

diff --git a/include/uapi/asm-generic/shmbuf.h b/include/uapi/asm-generic/shmbuf.h
new file mode 100644
index 000000000..2979b6dd2
--- /dev/null
+++ b/include/uapi/asm-generic/shmbuf.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __ASM_GENERIC_SHMBUF_H
+#define __ASM_GENERIC_SHMBUF_H
+
+#include <asm/bitsperlong.h>
+#include <asm/ipcbuf.h>
+#include <asm/posix_types.h>
+
+/*
+ * The shmid64_ds structure for x86 architecture.
+ * Note extra padding because this structure is passed back and forth
+ * between kernel and user space.
+ *
+ * shmid64_ds was originally meant to be architecture specific, but
+ * everyone just ended up making identical copies without specific
+ * optimizations, so we may just as well all use the same one.
+ *
+ * 64 bit architectures use a 64-bit long time field here, while
+ * 32 bit architectures have a pair of unsigned long values.
+ * On big-endian systems, the lower half is in the wrong place.
+ *
+ *
+ * Pad space is left for:
+ * - 2 miscellaneous 32-bit values
+ */
+
+struct shmid64_ds {
+	struct ipc64_perm	shm_perm;	/* operation perms */
+	__kernel_size_t		shm_segsz;	/* size of segment (bytes) */
+#if __BITS_PER_LONG == 64
+	long			shm_atime;	/* last attach time */
+	long			shm_dtime;	/* last detach time */
+	long			shm_ctime;	/* last change time */
+#else
+	unsigned long		shm_atime;	/* last attach time */
+	unsigned long		shm_atime_high;
+	unsigned long		shm_dtime;	/* last detach time */
+	unsigned long		shm_dtime_high;
+	unsigned long		shm_ctime;	/* last change time */
+	unsigned long		shm_ctime_high;
+#endif
+	__kernel_pid_t		shm_cpid;	/* pid of creator */
+	__kernel_pid_t		shm_lpid;	/* pid of last operator */
+	unsigned long		shm_nattch;	/* no. of current attaches */
+	unsigned long		__unused4;
+	unsigned long		__unused5;
+};
+
+struct shminfo64 {
+	unsigned long		shmmax;
+	unsigned long		shmmin;
+	unsigned long		shmmni;
+	unsigned long		shmseg;
+	unsigned long		shmall;
+	unsigned long		__unused1;
+	unsigned long		__unused2;
+	unsigned long		__unused3;
+	unsigned long		__unused4;
+};
+
+#endif /* __ASM_GENERIC_SHMBUF_H */