releases/4.14.40/tracing-fix-bad-use-of-igrab-in-trace_uprobe.c.patch

   1 From 0c92c7a3c5d416f47b32c5f20a611dfeca5d5f2e Mon Sep 17 00:00:00 2001
   2 From: Song Liu <songliubraving@fb.com>
   3 Date: Mon, 23 Apr 2018 10:21:34 -0700
   4 Subject: tracing: Fix bad use of igrab in trace_uprobe.c
   5
   6 From: Song Liu <songliubraving@fb.com>
   7
   8 commit 0c92c7a3c5d416f47b32c5f20a611dfeca5d5f2e upstream.
   9
  10 As Miklos reported and suggested:
  11
  12   This pattern repeats two times in trace_uprobe.c and in
  13   kernel/events/core.c as well:
  14
  15       ret = kern_path(filename, LOOKUP_FOLLOW, &path);
  16       if (ret)
  17           goto fail_address_parse;
  18
  19       inode = igrab(d_inode(path.dentry));
  20       path_put(&path);
  21
  22   And it's wrong.  You can only hold a reference to the inode if you
  23   have an active ref to the superblock as well (which is normally
  24   through path.mnt) or holding s_umount.
  25
  26   This way unmounting the containing filesystem while the tracepoint is
  27   active will give you the "VFS: Busy inodes after unmount..." message
  28   and a crash when the inode is finally put.
  29
  30   Solution: store path instead of inode.
  31
  32 This patch fixes two instances in trace_uprobe.c. struct path is added to
  33 struct trace_uprobe to keep the inode and containing mount point
  34 referenced.
  35
  36 Link: http://lkml.kernel.org/r/20180423172135.4050588-1-songliubraving@fb.com
  37
  38 Fixes: f3f096cfedf8 ("tracing: Provide trace events interface for uprobes")
  39 Fixes: 33ea4b24277b ("perf/core: Implement the 'perf_uprobe' PMU")
  40 Cc: stable@vger.kernel.org
  41 Cc: Ingo Molnar <mingo@redhat.com>
  42 Cc: Howard McLauchlan <hmclauchlan@fb.com>
  43 Cc: Josef Bacik <jbacik@fb.com>
  44 Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
  45 Acked-by: Miklos Szeredi <mszeredi@redhat.com>
  46 Reported-by: Miklos Szeredi <miklos@szeredi.hu>
  47 Signed-off-by: Song Liu <songliubraving@fb.com>
  48 Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
  49 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  50
  51 ---
  52  kernel/trace/trace_uprobe.c |   24 ++++++++++--------------
  53  1 file changed, 10 insertions(+), 14 deletions(-)
  54
  55 --- a/kernel/trace/trace_uprobe.c
  56 +++ b/kernel/trace/trace_uprobe.c
  57 @@ -55,6 +55,7 @@ struct trace_uprobe {
  58         struct list_head                list;
  59         struct trace_uprobe_filter      filter;
  60         struct uprobe_consumer          consumer;
  61 +       struct path                     path;
  62         struct inode                    *inode;
  63         char                            *filename;
  64         unsigned long                   offset;
  65 @@ -287,7 +288,7 @@ static void free_trace_uprobe(struct tra
  66         for (i = 0; i < tu->tp.nr_args; i++)
  67                 traceprobe_free_probe_arg(&tu->tp.args[i]);
  68
  69 -       iput(tu->inode);
  70 +       path_put(&tu->path);
  71         kfree(tu->tp.call.class->system);
  72         kfree(tu->tp.call.name);
  73         kfree(tu->filename);
  74 @@ -361,7 +362,6 @@ end:
  75  static int create_trace_uprobe(int argc, char **argv)
  76  {
  77         struct trace_uprobe *tu;
  78 -       struct inode *inode;
  79         char *arg, *event, *group, *filename;
  80         char buf[MAX_EVENT_NAME_LEN];
  81         struct path path;
  82 @@ -369,7 +369,6 @@ static int create_trace_uprobe(int argc,
  83         bool is_delete, is_return;
  84         int i, ret;
  85
  86 -       inode = NULL;
  87         ret = 0;
  88         is_delete = false;
  89         is_return = false;
  90 @@ -435,21 +434,16 @@ static int create_trace_uprobe(int argc,
  91         }
  92         /* Find the last occurrence, in case the path contains ':' too. */
  93         arg = strrchr(argv[1], ':');
  94 -       if (!arg) {
  95 -               ret = -EINVAL;
  96 -               goto fail_address_parse;
  97 -       }
  98 +       if (!arg)
  99 +               return -EINVAL;
 100
 101         *arg++ = '\0';
 102         filename = argv[1];
 103         ret = kern_path(filename, LOOKUP_FOLLOW, &path);
 104         if (ret)
 105 -               goto fail_address_parse;
 106 -
 107 -       inode = igrab(d_inode(path.dentry));
 108 -       path_put(&path);
 109 +               return ret;
 110
 111 -       if (!inode || !S_ISREG(inode->i_mode)) {
 112 +       if (!d_is_reg(path.dentry)) {
 113                 ret = -EINVAL;
 114                 goto fail_address_parse;
 115         }
 116 @@ -488,7 +482,7 @@ static int create_trace_uprobe(int argc,
 117                 goto fail_address_parse;
 118         }
 119         tu->offset = offset;
 120 -       tu->inode = inode;
 121 +       tu->path = path;
 122         tu->filename = kstrdup(filename, GFP_KERNEL);
 123
 124         if (!tu->filename) {
 125 @@ -556,7 +550,7 @@ error:
 126         return ret;
 127
 128  fail_address_parse:
 129 -       iput(inode);
 130 +       path_put(&path);
 131
 132         pr_info("Failed to parse address or file.\n");
 133
 134 @@ -935,6 +929,7 @@ probe_event_enable(struct trace_uprobe *
 135                 goto err_flags;
 136
 137         tu->consumer.filter = filter;
 138 +       tu->inode = d_real_inode(tu->path.dentry);
 139         ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
 140         if (ret)
 141                 goto err_buffer;
 142 @@ -980,6 +975,7 @@ probe_event_disable(struct trace_uprobe
 143         WARN_ON(!uprobe_filter_is_empty(&tu->filter));
 144
 145         uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
 146 +       tu->inode = NULL;
 147         tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
 148
 149         uprobe_buffer_disable();