From 5f81018753dfd4989e33ece1f0cb6b8aae498b82 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Thu, 15 Jun 2023 13:52:36 +0200 Subject: [PATCH 1/6] fprobe: Release rethook after the ftrace_ops is unregistered While running bpf selftests it's possible to get following fault: general protection fault, probably for non-canonical address \ 0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI ... Call Trace: fprobe_handler+0xc1/0x270 ? __pfx_bpf_testmod_init+0x10/0x10 ? __pfx_bpf_testmod_init+0x10/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_testmod_init+0x22/0x80 ? do_one_initcall+0x63/0x2e0 ? rcu_is_watching+0xd/0x40 ? kmalloc_trace+0xaf/0xc0 ? do_init_module+0x60/0x250 ? __do_sys_finit_module+0xac/0x120 ? do_syscall_64+0x37/0x90 ? entry_SYSCALL_64_after_hwframe+0x72/0xdc In unregister_fprobe function we can't release fp->rethook while it's possible there are some of its users still running on another cpu. Moving rethook_free call after fp->ops is unregistered with unregister_ftrace_function call. Link: https://lore.kernel.org/all/20230615115236.3476617-1-jolsa@kernel.org/ Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support") Cc: stable@vger.kernel.org Reviewed-by: Steven Rostedt (Google) Signed-off-by: Jiri Olsa Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/fprobe.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 18d36842faf5..0121e8c0d54e 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -364,19 +364,13 @@ int unregister_fprobe(struct fprobe *fp) fp->ops.saved_func != fprobe_kprobe_handler)) return -EINVAL; - /* - * rethook_free() starts disabling the rethook, but the rethook handlers - * may be running on other processors at this point. To make sure that all - * current running handlers are finished, call unregister_ftrace_function() - * after this. - */ - if (fp->rethook) - rethook_free(fp->rethook); - ret = unregister_ftrace_function(&fp->ops); if (ret < 0) return ret; + if (fp->rethook) + rethook_free(fp->rethook); + ftrace_free_filter(&fp->ops); return ret; From cf0a624dc706c306294c14e6b3e7694702f25191 Mon Sep 17 00:00:00 2001 From: "Tzvetomir Stoyanov (VMware)" Date: Mon, 3 Jul 2023 07:28:53 +0300 Subject: [PATCH 2/6] kernel/trace: Fix cleanup logic of enable_trace_eprobe The enable_trace_eprobe() function enables all event probes, attached to given trace probe. If an error occurs in enabling one of the event probes, all others should be roll backed. There is a bug in that roll back logic - instead of all event probes, only the failed one is disabled. Link: https://lore.kernel.org/all/20230703042853.1427493-1-tz.stoyanov@gmail.com/ Reported-by: Dan Carpenter Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events") Signed-off-by: Tzvetomir Stoyanov (VMware) Acked-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/trace_eprobe.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index 67e854979d53..3f04f0ffe0d7 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -675,6 +675,7 @@ static int enable_trace_eprobe(struct trace_event_call *call, struct trace_eprobe *ep; bool enabled; int ret = 0; + int cnt = 0; tp = trace_probe_primary_from_call(call); if (WARN_ON_ONCE(!tp)) @@ -698,12 +699,25 @@ static int enable_trace_eprobe(struct trace_event_call *call, if (ret) break; enabled = true; + cnt++; } if (ret) { /* Failed to enable one of them. Roll back all */ - if (enabled) - disable_eprobe(ep, file->tr); + if (enabled) { + /* + * It's a bug if one failed for something other than memory + * not being available but another eprobe succeeded. + */ + WARN_ON_ONCE(ret != -ENOMEM); + + list_for_each_entry(pos, trace_probe_probe_list(tp), list) { + ep = container_of(pos, struct trace_eprobe, tp); + disable_eprobe(ep, file->tr); + if (!--cnt) + break; + } + } if (file) trace_probe_remove_file(tp, file); else From 5f0c584daf7464f04114c65dd07269ee2bfedc13 Mon Sep 17 00:00:00 2001 From: Ze Gao Date: Mon, 3 Jul 2023 17:23:36 +0800 Subject: [PATCH 3/6] fprobe: add unlock to match a succeeded ftrace_test_recursion_trylock Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed because of some running kprobe. Link: https://lore.kernel.org/all/20230703092336.268371-1-zegao@tencent.com/ Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free") Reported-by: Yafang Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/ Signed-off-by: Ze Gao Acked-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Reviewed-by: Steven Rostedt (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/fprobe.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 0121e8c0d54e..58e4b3607aef 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip, if (unlikely(kprobe_running())) { fp->nmissed++; - return; + goto recursion_unlock; } kprobe_busy_begin(); __fprobe_handler(ip, parent_ip, ops, fregs); kprobe_busy_end(); + +recursion_unlock: ftrace_test_recursion_unlock(bit); } From e1164787f22b51010cfdc6a5e41b744435836b79 Mon Sep 17 00:00:00 2001 From: Li zeming Date: Wed, 5 Jul 2023 03:43:59 +0800 Subject: [PATCH 4/6] =?UTF-8?q?kprobes:=20Remove=20unnecessary=20=E2=80=98?= =?UTF-8?q?NULL=E2=80=99=20values=20from=20correct=5Fret=5Faddr?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The 'correct_ret_addr' pointer is always set in the later code, no need to initialize it at definition time. Link: https://lore.kernel.org/all/20230704194359.3124-1-zeming@nfschina.com/ Signed-off-by: Li zeming Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/kprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 00e177de91cc..fd713ab439c2 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -2007,9 +2007,9 @@ void __weak arch_kretprobe_fixup_return(struct pt_regs *regs, unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, void *frame_pointer) { - kprobe_opcode_t *correct_ret_addr = NULL; struct kretprobe_instance *ri = NULL; struct llist_node *first, *node = NULL; + kprobe_opcode_t *correct_ret_addr; struct kretprobe *rp; /* Find correct address and all nodes for this frame. */ From ed9492dfef8738ca68879f5690dda5a04f1897dc Mon Sep 17 00:00:00 2001 From: Li zeming Date: Wed, 12 Jul 2023 02:53:53 +0800 Subject: [PATCH 5/6] =?UTF-8?q?kernel:=20kprobes:=20Remove=20unnecessary?= =?UTF-8?q?=20=E2=80=980=E2=80=99=20values?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit it is assigned first, so it does not need to initialize the assignment. Link: https://lore.kernel.org/all/20230711185353.3218-1-zeming@nfschina.com/ Signed-off-by: Li zeming Acked-by: Masami Hiramatsu (Google) Signed-off-by: Masami Hiramatsu (Google) --- kernel/kprobes.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index fd713ab439c2..a009c8ccd8ea 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1072,7 +1072,7 @@ static int kprobe_ftrace_enabled; static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops, int *cnt) { - int ret = 0; + int ret; lockdep_assert_held(&kprobe_mutex); @@ -1110,7 +1110,7 @@ static int arm_kprobe_ftrace(struct kprobe *p) static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops, int *cnt) { - int ret = 0; + int ret; lockdep_assert_held(&kprobe_mutex); @@ -2692,7 +2692,7 @@ void kprobe_free_init_mem(void) static int __init init_kprobes(void) { - int i, err = 0; + int i, err; /* FIXME allocate the probe table, currently defined statically */ /* initialize all list heads */ From 195b9cb5b288fec1c871ef89f78cc9a7461aad3a Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Fri, 7 Jul 2023 23:03:19 +0900 Subject: [PATCH 6/6] fprobe: Ensure running fprobe_exit_handler() finished before calling rethook_free() Ensure running fprobe_exit_handler() has finished before calling rethook_free() in the unregister_fprobe() so that caller can free the fprobe right after unregister_fprobe(). unregister_fprobe() ensured that all running fprobe_entry/exit_handler() have finished by calling unregister_ftrace_function() which synchronizes RCU. But commit 5f81018753df ("fprobe: Release rethook after the ftrace_ops is unregistered") changed to call rethook_free() after unregister_ftrace_function(). So call rethook_stop() to make rethook disabled before unregister_ftrace_function() and ensure it again. Here is the possible code flow that can call the exit handler after unregister_fprobe(). ------ CPU1 CPU2 call unregister_fprobe(fp) ... __fprobe_handler() rethook_hook() on probed function unregister_ftrace_function() return from probed function rethook hooks find rh->handler == fprobe_exit_handler call fprobe_exit_handler() rethook_free(): set rh->handler = NULL; return from unreigster_fprobe; call fp->exit_handler() <- (*) ------ (*) At this point, the exit handler is called after returning from unregister_fprobe(). This fixes it as following; ------ CPU1 CPU2 call unregister_fprobe() ... rethook_stop(): set rh->handler = NULL; __fprobe_handler() rethook_hook() on probed function unregister_ftrace_function() return from probed function rethook hooks find rh->handler == NULL return from rethook rethook_free() return from unreigster_fprobe; ------ Link: https://lore.kernel.org/all/168873859949.156157.13039240432299335849.stgit@devnote2/ Fixes: 5f81018753df ("fprobe: Release rethook after the ftrace_ops is unregistered") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt (Google) --- include/linux/rethook.h | 1 + kernel/trace/fprobe.c | 3 +++ kernel/trace/rethook.c | 13 +++++++++++++ 3 files changed, 17 insertions(+) diff --git a/include/linux/rethook.h b/include/linux/rethook.h index c8ac1e5afcd1..bdbe6717f45a 100644 --- a/include/linux/rethook.h +++ b/include/linux/rethook.h @@ -59,6 +59,7 @@ struct rethook_node { }; struct rethook *rethook_alloc(void *data, rethook_handler_t handler); +void rethook_stop(struct rethook *rh); void rethook_free(struct rethook *rh); void rethook_add_node(struct rethook *rh, struct rethook_node *node); struct rethook_node *rethook_try_get(struct rethook *rh); diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 58e4b3607aef..2571f7f3d5f2 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -366,6 +366,9 @@ int unregister_fprobe(struct fprobe *fp) fp->ops.saved_func != fprobe_kprobe_handler)) return -EINVAL; + if (fp->rethook) + rethook_stop(fp->rethook); + ret = unregister_ftrace_function(&fp->ops); if (ret < 0) return ret; diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 60f6cb2b486b..468006cce7ca 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -53,6 +53,19 @@ static void rethook_free_rcu(struct rcu_head *head) kfree(rh); } +/** + * rethook_stop() - Stop using a rethook. + * @rh: the struct rethook to stop. + * + * Stop using a rethook to prepare for freeing it. If you want to wait for + * all running rethook handler before calling rethook_free(), you need to + * call this first and wait RCU, and call rethook_free(). + */ +void rethook_stop(struct rethook *rh) +{ + WRITE_ONCE(rh->handler, NULL); +} + /** * rethook_free() - Free struct rethook. * @rh: the struct rethook to be freed.