ksym_tracer: Remove trace_stat

trace_stat is problematic. Don't use it, use seqfile instead.

This fixes a race that reading the stat file is not protected by
any lock, which can lead to use after free.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B3AF203.40200@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 50 insertions, 77 deletions

diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index 67d79f709fc5..94103cdcf9d8 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -26,7 +26,6 @@
 #include <linux/fs.h>
 
 #include "trace_output.h"
-#include "trace_stat.h"
 #include "trace.h"
 
 #include <linux/hw_breakpoint.h>
@@ -444,103 +443,77 @@ struct tracer ksym_tracer __read_mostly =
         .print_line     = ksym_trace_output
 };
 
-__init static int init_ksym_trace(void)
-{
-        struct dentry *d_tracer;
-        struct dentry *entry;
-
-        d_tracer = tracing_init_dentry();
-        ksym_filter_entry_count = 0;
-
-        entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
-                                    NULL, &ksym_tracing_fops);
-        if (!entry)
-                pr_warning("Could not create debugfs "
-                           "'ksym_trace_filter' file\n");
-
-        return register_tracer(&ksym_tracer);
-}
-device_initcall(init_ksym_trace);
-
-
 #ifdef CONFIG_PROFILE_KSYM_TRACER
-static int ksym_tracer_stat_headers(struct seq_file *m)
+static int ksym_profile_show(struct seq_file *m, void *v)
 {
+        struct hlist_node *node;
+        struct trace_ksym *entry;
+        int access_type = 0;
+        char fn_name[KSYM_NAME_LEN];
+
         seq_puts(m, "  Access Type ");
         seq_puts(m, "  Symbol                                       Counter\n");
         seq_puts(m, "  ----------- ");
         seq_puts(m, "  ------                                       -------\n");
-        return 0;
-}
 
-static int ksym_tracer_stat_show(struct seq_file *m, void *v)
-{
-        struct hlist_node *stat = v;
-        struct trace_ksym *entry;
-        int access_type = 0;
-        char fn_name[KSYM_NAME_LEN];
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
 
-        entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
+                access_type = entry->attr.bp_type;
 
-        access_type = entry->attr.bp_type;
+                switch (access_type) {
+                case HW_BREAKPOINT_R:
+                        seq_puts(m, "  R           ");
+                        break;
+                case HW_BREAKPOINT_W:
+                        seq_puts(m, "  W           ");
+                        break;
+                case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
+                        seq_puts(m, "  RW          ");
+                        break;
+                default:
+                        seq_puts(m, "  NA          ");
+                }
 
-        switch (access_type) {
-        case HW_BREAKPOINT_R:
-                seq_puts(m, "  R           ");
-                break;
-        case HW_BREAKPOINT_W:
-                seq_puts(m, "  W           ");
-                break;
-        case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
-                seq_puts(m, "  RW          ");
-                break;
-        default:
-                seq_puts(m, "  NA          ");
+                if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
+                        seq_printf(m, "  %-36s", fn_name);
+                else
+                        seq_printf(m, "  %-36s", "<NA>");
+                seq_printf(m, " %15llu\n",
+                           (unsigned long long)atomic64_read(&entry->counter));
         }
-
-        if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
-                seq_printf(m, "  %-36s", fn_name);
-        else
-                seq_printf(m, "  %-36s", "<NA>");
-        seq_printf(m, " %15llu\n",
-                   (unsigned long long)atomic64_read(&entry->counter));
+        rcu_read_unlock();
 
         return 0;
 }
 
-static void *ksym_tracer_stat_start(struct tracer_stat *trace)
+static int ksym_profile_open(struct inode *node, struct file *file)
 {
-        return ksym_filter_head.first;
-}
-
-static void *
-ksym_tracer_stat_next(void *v, int idx)
-{
-        struct hlist_node *stat = v;
-
-        return stat->next;
+        return single_open(file, ksym_profile_show, NULL);
 }
 
-static struct tracer_stat ksym_tracer_stats = {
-        .name = "ksym_tracer",
-        .stat_start = ksym_tracer_stat_start,
-        .stat_next = ksym_tracer_stat_next,
-        .stat_headers = ksym_tracer_stat_headers,
-        .stat_show = ksym_tracer_stat_show
+static const struct file_operations ksym_profile_fops = {
+        .open           = ksym_profile_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
 };
+#endif /* CONFIG_PROFILE_KSYM_TRACER */
 
-__init static int ksym_tracer_stat_init(void)
+__init static int init_ksym_trace(void)
 {
-        int ret;
+        struct dentry *d_tracer;
 
-        ret = register_stat_tracer(&ksym_tracer_stats);
-        if (ret) {
-                printk(KERN_WARNING "Warning: could not register "
-                                    "ksym tracer stats\n");
-                return 1;
-        }
+        d_tracer = tracing_init_dentry();
 
-        return 0;
+        trace_create_file("ksym_trace_filter", 0644, d_tracer,
+                          NULL, &ksym_tracing_fops);
+
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+        trace_create_file("ksym_profile", 0444, d_tracer,
+                          NULL, &ksym_profile_fops);
+#endif
+
+        return register_tracer(&ksym_tracer);
 }
-fs_initcall(ksym_tracer_stat_init);
-#endif /* CONFIG_PROFILE_KSYM_TRACER */
+device_initcall(init_ksym_trace);