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Date: Mon, 26 Aug 2013 18:08:26 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Oleg Nesterov <oleg@...hat.com>, Steven Rostedt <rostedt@...dmis.org> Subject: [ 28/74] tracing: Change event_filter_read/write to verify i_private != NULL 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov <oleg@...hat.com> commit e2912b091c26b8ea95e5e00a43a7ac620f6c94a6 upstream. event_filter_read/write() are racy, ftrace_event_call can be already freed by trace_remove_event_call() callers. 1. Shift mutex_lock(event_mutex) from print/apply_event_filter to the callers. 2. Change the callers, event_filter_read() and event_filter_write() to read i_private under this mutex and abort if it is NULL. This fixes nothing, but now we can change debugfs_remove("filter") callers to nullify ->i_private and fix the the problem. Link: http://lkml.kernel.org/r/20130726172540.GA3619@redhat.com Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> Signed-off-by: Oleg Nesterov <oleg@...hat.com> Signed-off-by: Steven Rostedt <rostedt@...dmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- kernel/trace/trace_events.c | 26 +++++++++++++++++++------- kernel/trace/trace_events_filter.c | 17 ++++++----------- 2 files changed, 25 insertions(+), 18 deletions(-) --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1002,21 +1002,28 @@ static ssize_t event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { - struct ftrace_event_call *call = filp->private_data; + struct ftrace_event_call *call; struct trace_seq *s; - int r; + int r = -ENODEV; if (*ppos) return 0; s = kmalloc(sizeof(*s), GFP_KERNEL); + if (!s) return -ENOMEM; trace_seq_init(s); - print_event_filter(call, s); - r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len); + mutex_lock(&event_mutex); + call = event_file_data(filp); + if (call) + print_event_filter(call, s); + mutex_unlock(&event_mutex); + + if (call) + r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len); kfree(s); @@ -1027,9 +1034,9 @@ static ssize_t event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { - struct ftrace_event_call *call = filp->private_data; + struct ftrace_event_call *call; char *buf; - int err; + int err = -ENODEV; if (cnt >= PAGE_SIZE) return -EINVAL; @@ -1044,7 +1051,12 @@ event_filter_write(struct file *filp, co } buf[cnt] = '\0'; - err = apply_event_filter(call, buf); + mutex_lock(&event_mutex); + call = event_file_data(filp); + if (call) + err = apply_event_filter(call, buf); + mutex_unlock(&event_mutex); + free_page((unsigned long) buf); if (err < 0) return err; --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -631,17 +631,15 @@ static void append_filter_err(struct fil free_page((unsigned long) buf); } +/* caller must hold event_mutex */ void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s) { - struct event_filter *filter; + struct event_filter *filter = call->filter; - mutex_lock(&event_mutex); - filter = call->filter; if (filter && filter->filter_string) trace_seq_printf(s, "%s\n", filter->filter_string); else trace_seq_printf(s, "none\n"); - mutex_unlock(&event_mutex); } void print_subsystem_event_filter(struct event_subsystem *system, @@ -1835,23 +1833,22 @@ static int create_system_filter(struct e return err; } +/* caller must hold event_mutex */ int apply_event_filter(struct ftrace_event_call *call, char *filter_string) { struct event_filter *filter; - int err = 0; - - mutex_lock(&event_mutex); + int err; if (!strcmp(strstrip(filter_string), "0")) { filter_disable(call); filter = call->filter; if (!filter) - goto out_unlock; + return 0; RCU_INIT_POINTER(call->filter, NULL); /* Make sure the filter is not being used */ synchronize_sched(); __free_filter(filter); - goto out_unlock; + return 0; } err = create_filter(call, filter_string, true, &filter); @@ -1878,8 +1875,6 @@ int apply_event_filter(struct ftrace_eve __free_filter(tmp); } } -out_unlock: - mutex_unlock(&event_mutex); return err; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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