From: Ze Gao <zegao2021@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>,
Borislav Petkov <bp@alien8.de>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Heiko Carstens <hca@linux.ibm.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vasily Gorbik <gor@linux.ibm.com>,
x86@kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Conor Dooley <conor@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Yonghong Song <yhs@fb.com>, Ze Gao <zegao@tencent.com>
Subject: [PATCH v3 2/4] fprobe: make fprobe_kprobe_handler recursion free
Date: Wed, 17 May 2023 11:45:07 +0800 [thread overview]
Message-ID: <20230517034510.15639-3-zegao@tencent.com> (raw)
In-Reply-To: <20230517034510.15639-1-zegao@tencent.com>
Current implementation calls kprobe related functions before doing
ftrace recursion check in fprobe_kprobe_handler, which opens door
to kernel crash due to stack recursion if preempt_count_{add, sub}
is traceable in kprobe_busy_{begin, end}.
Things goes like this without this patch quoted from Steven:
"
fprobe_kprobe_handler() {
kprobe_busy_begin() {
preempt_disable() {
preempt_count_add() { <-- trace
fprobe_kprobe_handler() {
[ wash, rinse, repeat, CRASH!!! ]
"
By refactoring the common part out of fprobe_kprobe_handler and
fprobe_handler and call ftrace recursion detection at the very beginning,
the whole fprobe_kprobe_handler is free from recursion.
Signed-off-by: Ze Gao <zegao@tencent.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/linux-trace-kernel/20230516071830.8190-3-zegao@tencent.com
---
kernel/trace/fprobe.c | 59 ++++++++++++++++++++++++++++++++-----------
1 file changed, 44 insertions(+), 15 deletions(-)
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 9abb3905bc8e..097c740799ba 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -20,30 +20,22 @@ struct fprobe_rethook_node {
char data[];
};
-static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
- struct ftrace_ops *ops, struct ftrace_regs *fregs)
+static inline void __fprobe_handler(unsigned long ip, unsigned long
+ parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe_rethook_node *fpr;
struct rethook_node *rh = NULL;
struct fprobe *fp;
void *entry_data = NULL;
- int bit, ret;
+ int ret;
fp = container_of(ops, struct fprobe, ops);
- if (fprobe_disabled(fp))
- return;
-
- bit = ftrace_test_recursion_trylock(ip, parent_ip);
- if (bit < 0) {
- fp->nmissed++;
- return;
- }
if (fp->exit_handler) {
rh = rethook_try_get(fp->rethook);
if (!rh) {
fp->nmissed++;
- goto out;
+ return;
}
fpr = container_of(rh, struct fprobe_rethook_node, node);
fpr->entry_ip = ip;
@@ -61,23 +53,60 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
else
rethook_hook(rh, ftrace_get_regs(fregs), true);
}
-out:
+}
+
+static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+ struct fprobe *fp;
+ int bit;
+
+ fp = container_of(ops, struct fprobe, ops);
+ if (fprobe_disabled(fp))
+ return;
+
+ /* recursion detection has to go before any traceable function and
+ * all functions before this point should be marked as notrace
+ */
+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0) {
+ fp->nmissed++;
+ return;
+ }
+ __fprobe_handler(ip, parent_ip, ops, fregs);
ftrace_test_recursion_unlock(bit);
+
}
NOKPROBE_SYMBOL(fprobe_handler);
static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
- struct fprobe *fp = container_of(ops, struct fprobe, ops);
+ struct fprobe *fp;
+ int bit;
+
+ fp = container_of(ops, struct fprobe, ops);
+ if (fprobe_disabled(fp))
+ return;
+
+ /* recursion detection has to go before any traceable function and
+ * all functions called before this point should be marked as notrace
+ */
+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0) {
+ fp->nmissed++;
+ return;
+ }
if (unlikely(kprobe_running())) {
fp->nmissed++;
return;
}
+
kprobe_busy_begin();
- fprobe_handler(ip, parent_ip, ops, fregs);
+ __fprobe_handler(ip, parent_ip, ops, fregs);
kprobe_busy_end();
+ ftrace_test_recursion_unlock(bit);
}
static void fprobe_exit_handler(struct rethook_node *rh, void *data,
--
2.40.1
next prev parent reply other threads:[~2023-05-17 3:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 3:45 [PATCH v3 0/3] Make fprobe + rethook immune to recursion Ze Gao
2023-05-17 3:45 ` [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler Ze Gao
2023-05-17 11:59 ` Masami Hiramatsu
2023-05-18 2:40 ` Ze Gao
2023-05-17 3:45 ` Ze Gao [this message]
2023-05-17 10:47 ` [PATCH v3 2/4] fprobe: make fprobe_kprobe_handler recursion free Jiri Olsa
2023-05-17 11:42 ` Masami Hiramatsu
2023-05-17 12:30 ` Jiri Olsa
2023-05-17 14:27 ` Masami Hiramatsu
2023-05-18 0:16 ` Andrii Nakryiko
2023-05-18 2:49 ` Ze Gao
2023-06-28 7:16 ` Yafang Shao
2023-07-03 6:52 ` Ze Gao
2023-05-17 3:45 ` [PATCH v3 3/4] fprobe: add recursion detection in fprobe_exit_handler Ze Gao
2023-05-17 3:45 ` [PATCH v3 4/4] rethook, fprobe: do not trace rethook related functions Ze Gao
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