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Commit 27f29dbc authored by Song Liu's avatar Song Liu Committed by Greg Kroah-Hartman
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tracing: Fix bad use of igrab in trace_uprobe.c 

commit 0c92c7a3c5d416f47b32c5f20a611dfeca5d5f2e upstream.

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: 33ea4b24277b ("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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d86aaca9

kernel/trace/trace_uprobe.c

+10 −14
Original line number Original line Diff line number Diff line
@@ -55,6 +55,7 @@ struct trace_uprobe { 
	struct list_head		list;

	struct list_head		list;

	struct trace_uprobe_filter	filter;

	struct trace_uprobe_filter	filter;

	struct uprobe_consumer		consumer;

	struct uprobe_consumer		consumer;

	struct path			path;

	struct inode			*inode;

	struct inode			*inode;

	char				*filename;

	char				*filename;

	unsigned long			offset;

	unsigned long			offset;
@@ -287,7 +288,7 @@ static void free_trace_uprobe(struct trace_uprobe *tu) 
	for (i = 0; i < tu->tp.nr_args; i++)

	for (i = 0; i < tu->tp.nr_args; i++)

		traceprobe_free_probe_arg(&tu->tp.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.class->system);

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

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

	kfree(tu->filename);

	kfree(tu->filename);
@@ -361,7 +362,6 @@ static int register_trace_uprobe(struct trace_uprobe *tu) 
static int create_trace_uprobe(int argc, char **argv)

static int create_trace_uprobe(int argc, char **argv)

{

{

	struct trace_uprobe *tu;

	struct trace_uprobe *tu;

	struct inode *inode;

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

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

	char buf[MAX_EVENT_NAME_LEN];

	char buf[MAX_EVENT_NAME_LEN];

	struct path path;

	struct path path;
@@ -369,7 +369,6 @@ static int create_trace_uprobe(int argc, char **argv) 
	bool is_delete, is_return;

	bool is_delete, is_return;

	int i, ret;

	int i, ret;





	inode = NULL;

	ret = 0;

	ret = 0;

	is_delete = false;

	is_delete = false;

	is_return = false;

	is_return = false;
@@ -435,21 +434,16 @@ static int create_trace_uprobe(int argc, char **argv) 
	}

	}

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

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

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

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

	if (!arg) {

	if (!arg)

		ret = -EINVAL;

		return -EINVAL;

		goto fail_address_parse;

	}





	*arg++ = '\0';

	*arg++ = '\0';

	filename = argv[1];

	filename = argv[1];

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

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

	if (ret)

	if (ret)

		goto fail_address_parse;

		return ret;



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

	path_put(&path);





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

	if (!d_is_reg(path.dentry)) {

		ret = -EINVAL;

		ret = -EINVAL;

		goto fail_address_parse;

		goto fail_address_parse;

	}

	}
@@ -488,7 +482,7 @@ static int create_trace_uprobe(int argc, char **argv) 
		goto fail_address_parse;

		goto fail_address_parse;

	}

	}

	tu->offset = offset;

	tu->offset = offset;

	tu->inode = inode;

	tu->path = path;

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

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





	if (!tu->filename) {

	if (!tu->filename) {
@@ -556,7 +550,7 @@ static int create_trace_uprobe(int argc, char **argv) 
	return ret;

	return ret;





fail_address_parse:

fail_address_parse:

	iput(inode);

	path_put(&path);





	pr_info("Failed to parse address or file.\n");

	pr_info("Failed to parse address or file.\n");
@@ -935,6 +929,7 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file, 
		goto err_flags;

		goto err_flags;





	tu->consumer.filter = filter;

	tu->consumer.filter = filter;

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

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

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

	if (ret)

	if (ret)

		goto err_buffer;

		goto err_buffer;
@@ -980,6 +975,7 @@ probe_event_disable(struct trace_uprobe *tu, struct trace_event_file *file) 
	WARN_ON(!uprobe_filter_is_empty(&tu->filter));

	WARN_ON(!uprobe_filter_is_empty(&tu->filter));





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

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

	tu->inode = NULL;

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

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





	uprobe_buffer_disable();

	uprobe_buffer_disable();