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 --- lib/muldi3.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) create mode 100644 lib/muldi3.c (limited to 'lib/muldi3.c') diff --git a/lib/muldi3.c b/lib/muldi3.c new file mode 100644 index 000000000..9150ac130 --- /dev/null +++ b/lib/muldi3.c @@ -0,0 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + */ + +#include +#include + +#define W_TYPE_SIZE 32 + +#define __ll_B ((unsigned long) 1 << (W_TYPE_SIZE / 2)) +#define __ll_lowpart(t) ((unsigned long) (t) & (__ll_B - 1)) +#define __ll_highpart(t) ((unsigned long) (t) >> (W_TYPE_SIZE / 2)) + +/* If we still don't have umul_ppmm, define it using plain C. */ +#if !defined(umul_ppmm) +#define umul_ppmm(w1, w0, u, v) \ + do { \ + unsigned long __x0, __x1, __x2, __x3; \ + unsigned short __ul, __vl, __uh, __vh; \ + \ + __ul = __ll_lowpart(u); \ + __uh = __ll_highpart(u); \ + __vl = __ll_lowpart(v); \ + __vh = __ll_highpart(v); \ + \ + __x0 = (unsigned long) __ul * __vl; \ + __x1 = (unsigned long) __ul * __vh; \ + __x2 = (unsigned long) __uh * __vl; \ + __x3 = (unsigned long) __uh * __vh; \ + \ + __x1 += __ll_highpart(__x0); /* this can't give carry */\ + __x1 += __x2; /* but this indeed can */ \ + if (__x1 < __x2) /* did we get it? */ \ + __x3 += __ll_B; /* yes, add it in the proper pos */ \ + \ + (w1) = __x3 + __ll_highpart(__x1); \ + (w0) = __ll_lowpart(__x1) * __ll_B + __ll_lowpart(__x0);\ + } while (0) +#endif + +#if !defined(__umulsidi3) +#define __umulsidi3(u, v) ({ \ + DWunion __w; \ + umul_ppmm(__w.s.high, __w.s.low, u, v); \ + __w.ll; \ + }) +#endif + +long long notrace __muldi3(long long u, long long v) +{ + const DWunion uu = {.ll = u}; + const DWunion vv = {.ll = v}; + DWunion w = {.ll = __umulsidi3(uu.s.low, vv.s.low)}; + + w.s.high += ((unsigned long) uu.s.low * (unsigned long) vv.s.high + + (unsigned long) uu.s.high * (unsigned long) vv.s.low); + + return w.ll; +} +EXPORT_SYMBOL(__muldi3); -- cgit v1.3.1