6.11-stable review patch. If anyone has any objections, please let me know.
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From: Philo Lu lulie@linux.alibaba.com
[ Upstream commit 8aeaed21befc90f27f4fca6dd190850d97d2e9e3 ]
Pointers passed to tp_btf were trusted to be valid, but some tracepoints do take NULL pointer as input, such as trace_tcp_send_reset(). Then the invalid memory access cannot be detected by verifier.
This patch fix it by add a suffix "__nullable" to the unreliable argument. The suffix is shown in btf, and PTR_MAYBE_NULL will be added to nullable arguments. Then users must check the pointer before use it.
A problem here is that we use "btf_trace_##call" to search func_proto. As it is a typedef, argument names as well as the suffix are not recorded. To solve this, I use bpf_raw_event_map to find "__bpf_trace##template" from "btf_trace_##call", and then we can see the suffix.
Suggested-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Philo Lu lulie@linux.alibaba.com Link: https://lore.kernel.org/r/20240911033719.91468-2-lulie@linux.alibaba.com Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Stable-dep-of: cb4158ce8ec8 ("bpf: Mark raw_tp arguments with PTR_MAYBE_NULL") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/btf.c | 3 +++ kernel/bpf/verifier.c | 36 ++++++++++++++++++++++++++++++++---- 2 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 5f4f1d0bc23a4..76afa90814ddb 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6534,6 +6534,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, if (prog_args_trusted(prog)) info->reg_type |= PTR_TRUSTED;
+ if (btf_param_match_suffix(btf, &args[arg], "__nullable")) + info->reg_type |= PTR_MAYBE_NULL; + if (tgt_prog) { enum bpf_prog_type tgt_type;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3bee91db81f0a..0481915e63c21 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -28,6 +28,8 @@ #include <linux/cpumask.h> #include <linux/bpf_mem_alloc.h> #include <net/xdp.h> +#include <linux/trace_events.h> +#include <linux/kallsyms.h>
#include "disasm.h"
@@ -21308,11 +21310,13 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, { bool prog_extension = prog->type == BPF_PROG_TYPE_EXT; bool prog_tracing = prog->type == BPF_PROG_TYPE_TRACING; + char trace_symbol[KSYM_SYMBOL_LEN]; const char prefix[] = "btf_trace_"; + struct bpf_raw_event_map *btp; int ret = 0, subprog = -1, i; const struct btf_type *t; bool conservative = true; - const char *tname; + const char *tname, *fname; struct btf *btf; long addr = 0; struct module *mod = NULL; @@ -21443,10 +21447,34 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, return -EINVAL; } tname += sizeof(prefix) - 1; - t = btf_type_by_id(btf, t->type); - if (!btf_type_is_ptr(t)) - /* should never happen in valid vmlinux build */ + + /* The func_proto of "btf_trace_##tname" is generated from typedef without argument + * names. Thus using bpf_raw_event_map to get argument names. + */ + btp = bpf_get_raw_tracepoint(tname); + if (!btp) return -EINVAL; + fname = kallsyms_lookup((unsigned long)btp->bpf_func, NULL, NULL, NULL, + trace_symbol); + bpf_put_raw_tracepoint(btp); + + if (fname) + ret = btf_find_by_name_kind(btf, fname, BTF_KIND_FUNC); + + if (!fname || ret < 0) { + bpf_log(log, "Cannot find btf of tracepoint template, fall back to %s%s.\n", + prefix, tname); + t = btf_type_by_id(btf, t->type); + if (!btf_type_is_ptr(t)) + /* should never happen in valid vmlinux build */ + return -EINVAL; + } else { + t = btf_type_by_id(btf, ret); + if (!btf_type_is_func(t)) + /* should never happen in valid vmlinux build */ + return -EINVAL; + } + t = btf_type_by_id(btf, t->type); if (!btf_type_is_func_proto(t)) /* should never happen in valid vmlinux build */