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Commit 0c92c7a3 authored by Song Liu's avatar Song Liu Committed by Steven Rostedt (VMware)
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tracing: Fix bad use of igrab in trace_uprobe.c 

As Miklos reported and suggested:

  This pattern repeats two times in trace_uprobe.c and in
  kernel/events/core.c as well:

      ret = kern_path(filename, LOOKUP_FOLLOW, &path);
      if (ret)
          goto fail_address_parse;

      inode = igrab(d_inode(path.dentry));
      path_put(&path);

  And it's wrong.  You can only hold a reference to the inode if you
  have an active ref to the superblock as well (which is normally
  through path.mnt) or holding s_umount.

  This way unmounting the containing filesystem while the tracepoint is
  active will give you the "VFS: Busy inodes after unmount..." message
  and a crash when the inode is finally put.

  Solution: store path instead of inode.

This patch fixes two instances in trace_uprobe.c. struct path is added to
struct trace_uprobe to keep the inode and containing mount point
referenced.

Link: http://lkml.kernel.org/r/20180423172135.4050588-1-songliubraving@fb.com



Fixes: f3f096cf ("tracing: Provide trace events interface for uprobes")
Fixes: 33ea4b24 ("perf/core: Implement the 'perf_uprobe' PMU")
Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Howard McLauchlan <hmclauchlan@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Reported-by: default avatarMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 9a0fd675

kernel/trace/trace_uprobe.c

+14 −21
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ struct trace_uprobe { 
	struct list_head		list;

	struct trace_uprobe_filter	filter;

	struct uprobe_consumer		consumer;

	struct path			path;

	struct inode			*inode;

	char				*filename;

	unsigned long			offset;
@@ -289,7 +290,7 @@ static void free_trace_uprobe(struct trace_uprobe *tu) 
	for (i = 0; i < tu->tp.nr_args; i++)

		traceprobe_free_probe_arg(&tu->tp.args[i]);



	iput(tu->inode);

	path_put(&tu->path);

	kfree(tu->tp.call.class->system);

	kfree(tu->tp.call.name);

	kfree(tu->filename);
@@ -363,7 +364,6 @@ static int register_trace_uprobe(struct trace_uprobe *tu) 
static int create_trace_uprobe(int argc, char **argv)

{

	struct trace_uprobe *tu;

	struct inode *inode;

	char *arg, *event, *group, *filename;

	char buf[MAX_EVENT_NAME_LEN];

	struct path path;
@@ -371,7 +371,6 @@ static int create_trace_uprobe(int argc, char **argv) 
	bool is_delete, is_return;

	int i, ret;



	inode = NULL;

	ret = 0;

	is_delete = false;

	is_return = false;
@@ -437,21 +436,16 @@ static int create_trace_uprobe(int argc, char **argv) 
	}

	/* Find the last occurrence, in case the path contains ':' too. */

	arg = strrchr(argv[1], ':');

	if (!arg) {

		ret = -EINVAL;

		goto fail_address_parse;

	}

	if (!arg)

		return -EINVAL;



	*arg++ = '\0';

	filename = argv[1];

	ret = kern_path(filename, LOOKUP_FOLLOW, &path);

	if (ret)

		goto fail_address_parse;



	inode = igrab(d_real_inode(path.dentry));

	path_put(&path);

		return ret;



	if (!inode || !S_ISREG(inode->i_mode)) {

	if (!d_is_reg(path.dentry)) {

		ret = -EINVAL;

		goto fail_address_parse;

	}
@@ -490,7 +484,7 @@ static int create_trace_uprobe(int argc, char **argv) 
		goto fail_address_parse;

	}

	tu->offset = offset;

	tu->inode = inode;

	tu->path = path;

	tu->filename = kstrdup(filename, GFP_KERNEL);



	if (!tu->filename) {
@@ -558,7 +552,7 @@ static int create_trace_uprobe(int argc, char **argv) 
	return ret;



fail_address_parse:

	iput(inode);

	path_put(&path);



	pr_info("Failed to parse address or file.\n");
@@ -922,6 +916,7 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file, 
		goto err_flags;



	tu->consumer.filter = filter;

	tu->inode = d_real_inode(tu->path.dentry);

	ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);

	if (ret)

		goto err_buffer;
@@ -967,6 +962,7 @@ probe_event_disable(struct trace_uprobe *tu, struct trace_event_file *file) 
	WARN_ON(!uprobe_filter_is_empty(&tu->filter));



	uprobe_unregister(tu->inode, tu->offset, &tu->consumer);

	tu->inode = NULL;

	tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;



	uprobe_buffer_disable();
@@ -1337,7 +1333,6 @@ struct trace_event_call * 
create_local_trace_uprobe(char *name, unsigned long offs, bool is_return)

{

	struct trace_uprobe *tu;

	struct inode *inode;

	struct path path;

	int ret;
@@ -1345,11 +1340,8 @@ create_local_trace_uprobe(char *name, unsigned long offs, bool is_return) 
	if (ret)

		return ERR_PTR(ret);



	inode = igrab(d_inode(path.dentry));

	if (!d_is_reg(path.dentry)) {

		path_put(&path);



	if (!inode || !S_ISREG(inode->i_mode)) {

		iput(inode);

		return ERR_PTR(-EINVAL);

	}
@@ -1364,11 +1356,12 @@ create_local_trace_uprobe(char *name, unsigned long offs, bool is_return) 
	if (IS_ERR(tu)) {

		pr_info("Failed to allocate trace_uprobe.(%d)\n",

			(int)PTR_ERR(tu));

		path_put(&path);

		return ERR_CAST(tu);

	}



	tu->offset = offs;

	tu->inode = inode;

	tu->path = path;

	tu->filename = kstrdup(name, GFP_KERNEL);

	init_trace_event_call(tu, &tu->tp.call);