From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CCF4B1465A8; Tue, 25 Jun 2024 09:49:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719308953; cv=none; b=Ev8ikhCh8mpvfXIx4JzVb3fCrSbvwzuBPGDK54nTZoyTyG+Yg8r92jrvuvjIZ0cXhZj6c6JcrIvwJ+YPK9eo8wvGN84Ye0zT92H3/ljtyt/a11iMMIEX42ZTgjsFVP5ZLslLvPpxuTG7xCVsMycQ/KxYxIBejB/G5B/04MRN0WE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719308953; c=relaxed/simple; bh=+FjeeqaoshSNH2J0x1iTTNuJYX28QxenPkZAgE1Te8c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mX+xz3ZpKvdCVP04s2/ecXpQB6lC5u4fCkUjYSpiPe4G0TjhlMZtmLqq6TnHUfCKUmHVPUkqrJE2vXifAbPkLVpVABJc8zCJ3kbNK6Rrx8XhsRLBW4WboFljyw0gjFH4XdpCXPeKDLN0h1gyfypA/LPMWsPtJuAzDXeIB9sdBUA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=u/KCBAbg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="u/KCBAbg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50B60C32781; Tue, 25 Jun 2024 09:49:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1719308953; bh=+FjeeqaoshSNH2J0x1iTTNuJYX28QxenPkZAgE1Te8c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u/KCBAbgATXUSNQWBLusGkQR/N6bNbh3QGm0lcBpIxW1uZDeSPpzRdBZY2cGS9Cia 9/gTi+QVhPykJg83XqN+Fa2ZGWTr+ujGF06F+NvpwQr0DAO6ZChL5os66Zzug9mFJH d6XB1Hk023eumLhI/DksGCQm9qZo0+C5x9GDH9qc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stephen Brennan , "Masami Hiramatsu (Google)" , Guo Ren , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 6.6 044/192] kprobe/ftrace: bail out if ftrace was killed Date: Tue, 25 Jun 2024 11:31:56 +0200 Message-ID: <20240625085538.858639779@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240625085537.150087723@linuxfoundation.org> References: <20240625085537.150087723@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stephen Brennan [ Upstream commit 1a7d0890dd4a502a202aaec792a6c04e6e049547 ] If an error happens in ftrace, ftrace_kill() will prevent disarming kprobes. Eventually, the ftrace_ops associated with the kprobes will be freed, yet the kprobes will still be active, and when triggered, they will use the freed memory, likely resulting in a page fault and panic. This behavior can be reproduced quite easily, by creating a kprobe and then triggering a ftrace_kill(). For simplicity, we can simulate an ftrace error with a kernel module like [1]: [1]: https://github.com/brenns10/kernel_stuff/tree/master/ftrace_killer sudo perf probe --add commit_creds sudo perf trace -e probe:commit_creds # In another terminal make sudo insmod ftrace_killer.ko # calls ftrace_kill(), simulating bug # Back to perf terminal # ctrl-c sudo perf probe --del commit_creds After a short period, a page fault and panic would occur as the kprobe continues to execute and uses the freed ftrace_ops. While ftrace_kill() is supposed to be used only in extreme circumstances, it is invoked in FTRACE_WARN_ON() and so there are many places where an unexpected bug could be triggered, yet the system may continue operating, possibly without the administrator noticing. If ftrace_kill() does not panic the system, then we should do everything we can to continue operating, rather than leave a ticking time bomb. Link: https://lore.kernel.org/all/20240501162956.229427-1-stephen.s.brennan@oracle.com/ Signed-off-by: Stephen Brennan Acked-by: Masami Hiramatsu (Google) Acked-by: Guo Ren Reviewed-by: Steven Rostedt (Google) Signed-off-by: Masami Hiramatsu (Google) Signed-off-by: Sasha Levin --- arch/csky/kernel/probes/ftrace.c | 3 +++ arch/loongarch/kernel/ftrace_dyn.c | 3 +++ arch/parisc/kernel/ftrace.c | 3 +++ arch/powerpc/kernel/kprobes-ftrace.c | 3 +++ arch/riscv/kernel/probes/ftrace.c | 3 +++ arch/s390/kernel/ftrace.c | 3 +++ arch/x86/kernel/kprobes/ftrace.c | 3 +++ include/linux/kprobes.h | 7 +++++++ kernel/kprobes.c | 6 ++++++ kernel/trace/ftrace.c | 1 + 10 files changed, 35 insertions(+) diff --git a/arch/csky/kernel/probes/ftrace.c b/arch/csky/kernel/probes/ftrace.c index 834cffcfbce32..7ba4b98076de1 100644 --- a/arch/csky/kernel/probes/ftrace.c +++ b/arch/csky/kernel/probes/ftrace.c @@ -12,6 +12,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe_ctlblk *kcb; struct pt_regs *regs; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c index 73858c9029cc9..bff058317062e 100644 --- a/arch/loongarch/kernel/ftrace_dyn.c +++ b/arch/loongarch/kernel/ftrace_dyn.c @@ -287,6 +287,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe *p; struct kprobe_ctlblk *kcb; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c index 621a4b386ae4f..c91f9c2e61ed2 100644 --- a/arch/parisc/kernel/ftrace.c +++ b/arch/parisc/kernel/ftrace.c @@ -206,6 +206,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe *p; int bit; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c index 072ebe7f290ba..f8208c027148f 100644 --- a/arch/powerpc/kernel/kprobes-ftrace.c +++ b/arch/powerpc/kernel/kprobes-ftrace.c @@ -21,6 +21,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, struct pt_regs *regs; int bit; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(nip, parent_nip); if (bit < 0) return; diff --git a/arch/riscv/kernel/probes/ftrace.c b/arch/riscv/kernel/probes/ftrace.c index 7142ec42e889f..a69dfa610aa85 100644 --- a/arch/riscv/kernel/probes/ftrace.c +++ b/arch/riscv/kernel/probes/ftrace.c @@ -11,6 +11,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe_ctlblk *kcb; int bit; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index c46381ea04ecb..7f6f8c438c265 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -296,6 +296,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe *p; int bit; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index dd2ec14adb77b..15af7e98e161a 100644 --- a/arch/x86/kernel/kprobes/ftrace.c +++ b/arch/x86/kernel/kprobes/ftrace.c @@ -21,6 +21,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct kprobe_ctlblk *kcb; int bit; + if (unlikely(kprobe_ftrace_disabled)) + return; + bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 8de5d51a0b5e7..45d5b0a76b0bd 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -383,11 +383,15 @@ static inline void wait_for_kprobe_optimizer(void) { } extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs); extern int arch_prepare_kprobe_ftrace(struct kprobe *p); +/* Set when ftrace has been killed: kprobes on ftrace must be disabled for safety */ +extern bool kprobe_ftrace_disabled __read_mostly; +extern void kprobe_ftrace_kill(void); #else static inline int arch_prepare_kprobe_ftrace(struct kprobe *p) { return -EINVAL; } +static inline void kprobe_ftrace_kill(void) {} #endif /* CONFIG_KPROBES_ON_FTRACE */ /* Get the kprobe at this addr (if any) - called with preemption disabled */ @@ -496,6 +500,9 @@ static inline void kprobe_flush_task(struct task_struct *tk) static inline void kprobe_free_init_mem(void) { } +static inline void kprobe_ftrace_kill(void) +{ +} static inline int disable_kprobe(struct kprobe *kp) { return -EOPNOTSUPP; diff --git a/kernel/kprobes.c b/kernel/kprobes.c index c2841e5957130..c8720bed8ed6a 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1068,6 +1068,7 @@ static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = { static int kprobe_ipmodify_enabled; static int kprobe_ftrace_enabled; +bool kprobe_ftrace_disabled; static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops, int *cnt) @@ -1136,6 +1137,11 @@ static int disarm_kprobe_ftrace(struct kprobe *p) ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops, ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled); } + +void kprobe_ftrace_kill() +{ + kprobe_ftrace_disabled = true; +} #else /* !CONFIG_KPROBES_ON_FTRACE */ static inline int arm_kprobe_ftrace(struct kprobe *p) { diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 2f80239348f5d..175eba24f5629 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -7899,6 +7899,7 @@ void ftrace_kill(void) ftrace_disabled = 1; ftrace_enabled = 0; ftrace_trace_function = ftrace_stub; + kprobe_ftrace_kill(); } /** -- 2.43.0