From b022f0c7e404887a7c5229788fc99eff9f9a80d5 Mon Sep 17 00:00:00 2001 From: Francis Laniel Date: Fri, 20 Oct 2023 13:42:49 +0300 Subject: [PATCH 1/2] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols When a kprobe is attached to a function that's name is not unique (is static and shares the name with other functions in the kernel), the kprobe is attached to the first function it finds. This is a bug as the function that it is attaching to is not necessarily the one that the user wants to attach to. Instead of blindly picking a function to attach to what is ambiguous, error with EADDRNOTAVAIL to let the user know that this function is not unique, and that the user must use another unique function with an address offset to get to the function they want to attach to. Link: https://lore.kernel.org/all/20231020104250.9537-2-flaniel@linux.microsoft.com/ Cc: stable@vger.kernel.org Fixes: 413d37d1eb69 ("tracing: Add kprobe-based event tracer") Suggested-by: Masami Hiramatsu Signed-off-by: Francis Laniel Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/trace_kprobe.c | 63 +++++++++++++++++++++++++++++++++++++ kernel/trace/trace_probe.h | 1 + 2 files changed, 64 insertions(+) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 3d7a180a8427..a8fef6ab0872 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = { .priority = 1 /* Invoked after kprobe module callback */ }; +static int count_symbols(void *data, unsigned long unused) +{ + unsigned int *count = data; + + (*count)++; + + return 0; +} + +static unsigned int number_of_same_symbols(char *func_name) +{ + unsigned int count; + + count = 0; + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); + + return count; +} + static int __trace_kprobe_create(int argc, const char *argv[]) { /* @@ -836,6 +855,31 @@ static int __trace_kprobe_create(int argc, const char *argv[]) } } + if (symbol && !strchr(symbol, ':')) { + unsigned int count; + + count = number_of_same_symbols(symbol); + if (count > 1) { + /* + * Users should use ADDR to remove the ambiguity of + * using KSYM only. + */ + trace_probe_log_err(0, NON_UNIQ_SYMBOL); + ret = -EADDRNOTAVAIL; + + goto error; + } else if (count == 0) { + /* + * We can return ENOENT earlier than when register the + * kprobe. + */ + trace_probe_log_err(0, BAD_PROBE_ADDR); + ret = -ENOENT; + + goto error; + } + } + trace_probe_log_set_index(0); if (event) { ret = traceprobe_parse_event_name(&event, &group, gbuf, @@ -1695,6 +1739,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) } #ifdef CONFIG_PERF_EVENTS + /* create a trace_kprobe, but don't add it to global lists */ struct trace_event_call * create_local_trace_kprobe(char *func, void *addr, unsigned long offs, @@ -1705,6 +1750,24 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, int ret; char *event; + if (func) { + unsigned int count; + + count = number_of_same_symbols(func); + if (count > 1) + /* + * Users should use addr to remove the ambiguity of + * using func only. + */ + return ERR_PTR(-EADDRNOTAVAIL); + else if (count == 0) + /* + * We can return ENOENT earlier than when register the + * kprobe. + */ + return ERR_PTR(-ENOENT); + } + /* * local trace_kprobes are not added to dyn_event, so they are never * searched in find_trace_kprobe(). Therefore, there is no concern of diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 02b432ae7513..850d9ecb6765 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -450,6 +450,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(BAD_MAXACT, "Invalid maxactive number"), \ C(MAXACT_TOO_BIG, "Maxactive is too big"), \ C(BAD_PROBE_ADDR, "Invalid probed address or symbol"), \ + C(NON_UNIQ_SYMBOL, "The symbol is not unique"), \ C(BAD_RETPROBE, "Retprobe address must be an function entry"), \ C(NO_TRACEPOINT, "Tracepoint is not found"), \ C(BAD_ADDR_SUFFIX, "Invalid probed address suffix"), \ From 03b80ff8023adae6780e491f66e932df8165e3a0 Mon Sep 17 00:00:00 2001 From: Francis Laniel Date: Fri, 20 Oct 2023 13:42:50 +0300 Subject: [PATCH 2/2] selftests/ftrace: Add new test case which checks non unique symbol If name_show() is non unique, this test will try to install a kprobe on this function which should fail returning EADDRNOTAVAIL. On kernel where name_show() is not unique, this test is skipped. Link: https://lore.kernel.org/all/20231020104250.9537-3-flaniel@linux.microsoft.com/ Cc: stable@vger.kernel.org Signed-off-by: Francis Laniel Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- .../ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc | 13 +++++++++++++ 1 file changed, 13 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc new file mode 100644 index 000000000000..bc9514428dba --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc @@ -0,0 +1,13 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: Test failure of registering kprobe on non unique symbol +# requires: kprobe_events + +SYMBOL='name_show' + +# We skip this test on kernel where SYMBOL is unique or does not exist. +if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}" /proc/kallsyms)" -le '1' ]; then + exit_unsupported +fi + +! echo "p:test_non_unique ${SYMBOL}" > kprobe_events