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03b77e17ae
__kptr meant to store PTR_UNTRUSTED kernel pointers inside bpf maps. The concept felt useful, but didn't get much traction, since bpf_rdonly_cast() was added soon after and bpf programs received a simpler way to access PTR_UNTRUSTED kernel pointers without going through restrictive __kptr usage. Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted to indicate its intended usage. The main goal of __kptr_untrusted was to read/write such pointers directly while bpf_kptr_xchg was a mechanism to access refcnted kernel pointers. The next patch will allow RCU protected __kptr access with direct read. At that point __kptr_untrusted will be deprecated. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-2-alexei.starovoitov@gmail.com
117 lines
2.4 KiB
C
117 lines
2.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <vmlinux.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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struct map_value {
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struct prog_test_ref_kfunc __kptr *ptr;
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};
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__type(key, int);
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__type(value, struct map_value);
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__uint(max_entries, 16);
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} array_map SEC(".maps");
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extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
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extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
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static __noinline int cb1(void *map, void *key, void *value, void *ctx)
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{
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void *p = *(void **)ctx;
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bpf_kfunc_call_test_release(p);
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/* Without the fix this would cause underflow */
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return 0;
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}
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SEC("?tc")
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int underflow_prog(void *ctx)
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{
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struct prog_test_ref_kfunc *p;
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unsigned long sl = 0;
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p = bpf_kfunc_call_test_acquire(&sl);
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if (!p)
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return 0;
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bpf_for_each_map_elem(&array_map, cb1, &p, 0);
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return 0;
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}
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static __always_inline int cb2(void *map, void *key, void *value, void *ctx)
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{
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unsigned long sl = 0;
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*(void **)ctx = bpf_kfunc_call_test_acquire(&sl);
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/* Without the fix this would leak memory */
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return 0;
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}
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SEC("?tc")
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int leak_prog(void *ctx)
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{
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struct prog_test_ref_kfunc *p;
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struct map_value *v;
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unsigned long sl;
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v = bpf_map_lookup_elem(&array_map, &(int){0});
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if (!v)
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return 0;
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p = NULL;
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bpf_for_each_map_elem(&array_map, cb2, &p, 0);
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p = bpf_kptr_xchg(&v->ptr, p);
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if (p)
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bpf_kfunc_call_test_release(p);
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return 0;
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}
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static __always_inline int cb(void *map, void *key, void *value, void *ctx)
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{
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return 0;
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}
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static __always_inline int cb3(void *map, void *key, void *value, void *ctx)
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{
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unsigned long sl = 0;
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void *p;
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bpf_kfunc_call_test_acquire(&sl);
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bpf_for_each_map_elem(&array_map, cb, &p, 0);
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/* It should only complain here, not in cb. This is why we need
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* callback_ref to be set to frameno.
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*/
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return 0;
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}
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SEC("?tc")
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int nested_cb(void *ctx)
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{
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struct prog_test_ref_kfunc *p;
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unsigned long sl = 0;
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int sp = 0;
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p = bpf_kfunc_call_test_acquire(&sl);
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if (!p)
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return 0;
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bpf_for_each_map_elem(&array_map, cb3, &sp, 0);
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bpf_kfunc_call_test_release(p);
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return 0;
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}
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SEC("?tc")
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int non_cb_transfer_ref(void *ctx)
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{
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struct prog_test_ref_kfunc *p;
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unsigned long sl = 0;
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p = bpf_kfunc_call_test_acquire(&sl);
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if (!p)
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return 0;
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cb1(NULL, NULL, NULL, &p);
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bpf_kfunc_call_test_acquire(&sl);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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