From 9ef16693aff8137faa21d16ffe65bb9832d24d71 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Fri, 11 Oct 2019 17:56:57 -0400 Subject: ftrace: Get a reference counter for the trace_array on filter files The ftrace set_ftrace_filter and set_ftrace_notrace files are specific for an instance now. They need to take a reference to the instance otherwise there could be a race between accessing the files and deleting the instance. It wasn't until the :mod: caching where these file operations started referencing the trace_array directly. Cc: stable@vger.kernel.org Fixes: 673feb9d76ab3 ("ftrace: Add :mod: caching infrastructure to trace_array") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) (limited to 'kernel/trace/ftrace.c') diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 62a50bf399d6..32c2eb167de0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3540,21 +3540,22 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, struct ftrace_hash *hash; struct list_head *mod_head; struct trace_array *tr = ops->private; - int ret = 0; + int ret = -ENOMEM; ftrace_ops_init(ops); if (unlikely(ftrace_disabled)) return -ENODEV; + if (tr && trace_array_get(tr) < 0) + return -ENODEV; + iter = kzalloc(sizeof(*iter), GFP_KERNEL); if (!iter) - return -ENOMEM; + goto out; - if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) { - kfree(iter); - return -ENOMEM; - } + if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) + goto out; iter->ops = ops; iter->flags = flag; @@ -3584,13 +3585,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, if (!iter->hash) { trace_parser_put(&iter->parser); - kfree(iter); - ret = -ENOMEM; goto out_unlock; } } else iter->hash = hash; + ret = 0; + if (file->f_mode & FMODE_READ) { iter->pg = ftrace_pages_start; @@ -3602,7 +3603,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, /* Failed */ free_ftrace_hash(iter->hash); trace_parser_put(&iter->parser); - kfree(iter); } } else file->private_data = iter; @@ -3610,6 +3610,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, out_unlock: mutex_unlock(&ops->func_hash->regex_lock); + out: + if (ret) { + kfree(iter); + if (tr) + trace_array_put(tr); + } + return ret; } @@ -5037,6 +5044,8 @@ int ftrace_regex_release(struct inode *inode, struct file *file) mutex_unlock(&iter->ops->func_hash->regex_lock); free_ftrace_hash(iter->hash); + if (iter->tr) + trace_array_put(iter->tr); kfree(iter); return 0; -- cgit v1.2.3 From 8530dec63e7b486e3761cc3d74a22de301845ff5 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Fri, 11 Oct 2019 17:39:57 -0400 Subject: tracing: Add tracing_check_open_get_tr() Currently, most files in the tracefs directory test if tracing_disabled is set. If so, it should return -ENODEV. The tracing_disabled is called when tracing is found to be broken. Originally it was done in case the ring buffer was found to be corrupted, and we wanted to prevent reading it from crashing the kernel. But it's also called if a tracing selftest fails on boot. It's a one way switch. That is, once it is triggered, tracing is disabled until reboot. As most tracefs files can also be used by instances in the tracefs directory, they need to be carefully done. Each instance has a trace_array associated to it, and when the instance is removed, the trace_array is freed. But if an instance is opened with a reference to the trace_array, then it requires looking up the trace_array to get its ref counter (as there could be a race with it being deleted and the open itself). Once it is found, a reference is added to prevent the instance from being removed (and the trace_array associated with it freed). Combine the two checks (tracing_disabled and trace_array_get()) into a single helper function. This will also make it easier to add lockdown to tracefs later. Link: http://lkml.kernel.org/r/20191011135458.7399da44@gandalf.local.home Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'kernel/trace/ftrace.c') diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 32c2eb167de0..8b765a55e01c 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -3547,7 +3547,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag, if (unlikely(ftrace_disabled)) return -ENODEV; - if (tr && trace_array_get(tr) < 0) + if (tracing_check_open_get_tr(tr)) return -ENODEV; iter = kzalloc(sizeof(*iter), GFP_KERNEL); @@ -6546,8 +6546,9 @@ ftrace_pid_open(struct inode *inode, struct file *file) struct seq_file *m; int ret = 0; - if (trace_array_get(tr) < 0) - return -ENODEV; + ret = tracing_check_open_get_tr(tr); + if (ret) + return ret; if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) -- cgit v1.2.3 From 17911ff38aa58d3c95c07589dbf5d3564c4cf3c5 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Fri, 11 Oct 2019 17:22:50 -0400 Subject: tracing: Add locked_down checks to the open calls of files created for tracefs Added various checks on open tracefs calls to see if tracefs is in lockdown mode, and if so, to return -EPERM. Note, the event format files (which are basically standard on all machines) as well as the enabled_functions file (which shows what is currently being traced) are not lockde down. Perhaps they should be, but it seems counter intuitive to lockdown information to help you know if the system has been modified. Link: http://lkml.kernel.org/r/CAHk-=wj7fGPKUspr579Cii-w_y60PtRaiDgKuxVtBAMK0VNNkA@mail.gmail.com Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) (limited to 'kernel/trace/ftrace.c') diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 8b765a55e01c..f296d89be757 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include #include @@ -3486,6 +3487,11 @@ static int ftrace_avail_open(struct inode *inode, struct file *file) { struct ftrace_iterator *iter; + int ret; + + ret = security_locked_down(LOCKDOWN_TRACEFS); + if (ret) + return ret; if (unlikely(ftrace_disabled)) return -ENODEV; @@ -3505,6 +3511,15 @@ ftrace_enabled_open(struct inode *inode, struct file *file) { struct ftrace_iterator *iter; + /* + * This shows us what functions are currently being + * traced and by what. Not sure if we want lockdown + * to hide such critical information for an admin. + * Although, perhaps it can show information we don't + * want people to see, but if something is tracing + * something, we probably want to know about it. + */ + iter = __seq_open_private(file, &show_ftrace_seq_ops, sizeof(*iter)); if (!iter) return -ENOMEM; @@ -3625,6 +3640,7 @@ ftrace_filter_open(struct inode *inode, struct file *file) { struct ftrace_ops *ops = inode->i_private; + /* Checks for tracefs lockdown */ return ftrace_regex_open(ops, FTRACE_ITER_FILTER | FTRACE_ITER_DO_PROBES, inode, file); @@ -3635,6 +3651,7 @@ ftrace_notrace_open(struct inode *inode, struct file *file) { struct ftrace_ops *ops = inode->i_private; + /* Checks for tracefs lockdown */ return ftrace_regex_open(ops, FTRACE_ITER_NOTRACE, inode, file); } @@ -5203,9 +5220,13 @@ static int __ftrace_graph_open(struct inode *inode, struct file *file, struct ftrace_graph_data *fgd) { - int ret = 0; + int ret; struct ftrace_hash *new_hash = NULL; + ret = security_locked_down(LOCKDOWN_TRACEFS); + if (ret) + return ret; + if (file->f_mode & FMODE_WRITE) { const int size_bits = FTRACE_HASH_DEFAULT_BITS; -- cgit v1.2.3