From 33a154a96e71a34a1bcca9f40da343dbbf7b38b4 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 1 Oct 2026 14:52:55 +0000 Subject: selftests/bpf: Test packet range of pointers sharing an id Add tests where two packet pointers share an id and tightening one pointer's umax from its var_off would put it less than their constant distance from the other's umax: with an index & 0x38 capped at 50, the base pointer keeps umax 50, so the pointer 8 bytes further on must keep umax 58, even though its known bits allow at most 56. These refused a valid program or accepted an out-of-bounds access before the fix: - check the advanced copy, load through the base: valid, was refused; - check the base, load the byte at base + 1 through a copy advanced by 8: was accepted; - check base + 4, load 4 bytes at base + 2 through base + 8: reads two bytes past the checked range, was accepted; - the same as the second with data_meta pointers checked against data: was accepted. These pass with and without the fix and cover nearby paths: - subtract an unknown scalar from a checked pointer and load below it (the range is kept across a new id); - reach a load through two paths whose checks cover 8 and 7 bytes after the loaded pointer; the second path must not be pruned by the first; - spill a copy of a pointer, check the pointer, fill the copy and load one byte past the checked range: the load is refused, and the copy has the range of the check. Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com Signed-off-by: Kumar Kartikeya Dwivedi --- lib/is_single_threaded.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 lib/is_single_threaded.c (limited to 'lib/is_single_threaded.c') diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c new file mode 100644 index 000000000..8c98b20bf --- /dev/null +++ b/lib/is_single_threaded.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Function to determine if a thread group is single threaded or not + * + * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * - Derived from security/selinux/hooks.c + */ +#include +#include +#include + +/* + * Returns true if the task does not share ->mm with another thread/process. + */ +bool current_is_single_threaded(void) +{ + struct task_struct *task = current; + struct mm_struct *mm = task->mm; + struct task_struct *p, *t; + bool ret; + + if (atomic_read(&task->signal->live) != 1) + return false; + + if (atomic_read(&mm->mm_users) == 1) + return true; + + ret = false; + rcu_read_lock(); + for_each_process(p) { + if (unlikely(p->flags & PF_KTHREAD)) + continue; + if (unlikely(p == task->group_leader)) + continue; + + for_each_thread(p, t) { + if (unlikely(t->mm == mm)) + goto found; + if (likely(t->mm)) + break; + /* + * t->mm == NULL. Make sure next_thread/next_task + * will see other CLONE_VM tasks which might be + * forked before exiting. + */ + smp_rmb(); + } + } + ret = true; +found: + rcu_read_unlock(); + + return ret; +} -- cgit v1.3.1