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 --- include/uapi/asm-generic/sembuf.h | 45 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 include/uapi/asm-generic/sembuf.h (limited to 'include/uapi/asm-generic/sembuf.h') diff --git a/include/uapi/asm-generic/sembuf.h b/include/uapi/asm-generic/sembuf.h new file mode 100644 index 000000000..f54e48fc9 --- /dev/null +++ b/include/uapi/asm-generic/sembuf.h @@ -0,0 +1,45 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef __ASM_GENERIC_SEMBUF_H +#define __ASM_GENERIC_SEMBUF_H + +#include +#include + +/* + * The semid64_ds structure for most architectures (though it came from x86_32 + * originally). Note extra padding because this structure is passed back and + * forth between kernel and user space. + * + * semid64_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 padding is in the wrong place for + * historic reasons, so user space has to reconstruct a time_t + * value using + * + * user_semid_ds.sem_otime = kernel_semid64_ds.sem_otime + + * ((long long)kernel_semid64_ds.sem_otime_high << 32) + * + * Pad space is left for 2 miscellaneous 32-bit values + */ +struct semid64_ds { + struct ipc64_perm sem_perm; /* permissions .. see ipc.h */ +#if __BITS_PER_LONG == 64 + long sem_otime; /* last semop time */ + long sem_ctime; /* last change time */ +#else + unsigned long sem_otime; /* last semop time */ + unsigned long sem_otime_high; + unsigned long sem_ctime; /* last change time */ + unsigned long sem_ctime_high; +#endif + unsigned long sem_nsems; /* no. of semaphores in array */ + unsigned long __unused3; + unsigned long __unused4; +}; + +#endif /* __ASM_GENERIC_SEMBUF_H */ -- cgit v1.3.1