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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6aa1d2b0899sm4203118a12.31.2026.09.17.14.24.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Sep 2026 14:24:10 -0700 (PDT) From: David Carlier To: mhiramat@kernel.org, rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com, martin@kaiser.cx, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, David Carlier Subject: [PATCH v2] fprobe: Terminate the fgraph_data list when the reservation is not filled Date: Thu, 17 Sep 2026 22:24:07 +0100 Message-ID: <20260917212407.384468-1-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit fprobe_fgraph_entry() reserves shadow stack space for every fprobe with an exit handler, but only fills it for those whose entry handler returns 0. fgraph_reserve_data() does not clear the area, so fprobe_return() parses the unused tail as headers left over from an earlier call, and an exit handler can run twice or despite its entry handler asking to skip it. Write a zero word after the last entry to terminate the walk. A zeroed slot does not decode to a NULL fprobe on the arches that encode the header into one unsigned long, since arch_decode_fprobe_header_fp() ORs in FPROBE_HEADER_MSB_PATTERN, so make read_fprobe_header() return NULL for a zeroed slot. Fixes: e0a384434ae1 ("tracing: fprobe: do not zero out unused fgraph_data") Cc: stable@vger.kernel.org Suggested-by: Masami Hiramatsu (Google) Signed-off-by: David Carlier --- kernel/trace/fprobe.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 1e9b00997ff2..9f2d98181779 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -171,6 +171,11 @@ static inline bool write_fprobe_header(unsigned long *stack, static inline void read_fprobe_header(unsigned long *stack, struct fprobe **fp, unsigned int *size_words) { + if (!*stack) { + *fp = NULL; + *size_words = 0; + return; + } *fp = arch_decode_fprobe_header_fp(*stack); *size_words = arch_decode_fprobe_header_size(*stack); } @@ -203,6 +208,12 @@ static inline void read_fprobe_header(unsigned long *stack, { struct __fprobe_header *fph = (struct __fprobe_header *)stack; + if (!*stack) { + *fp = NULL; + *size_words = 0; + return; + } + *fp = fph->fp; *size_words = fph->size_words; } @@ -635,6 +646,10 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops } } + /* Terminate the list, fgraph_reserve_data() does not clear it. */ + if (used && used < reserved_words) + fgraph_data[used] = 0; + /* If any exit_handler is set, data must be used. */ return used != 0; } -- 2.55.0