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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: f3f096cfed ("tracing: Provide trace events interface for uprobes")
Fixes: 33ea4b2427 ("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: Miklos Szeredi <mszeredi@redhat.com>
Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Song Liu 2018-04-23 10:21:34 -07:00 committed by Steven Rostedt (VMware)
parent 9a0fd67530
commit 0c92c7a3c5
1 changed files with 14 additions and 21 deletions
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35
kernel/trace/trace_uprobe.c
View File

@ -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 @@ end:
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;
return ret;
inode = igrab(d_real_inode(path.dentry));
path_put(&path);
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 @@ error:
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));
path_put(&path);
if (!inode || !S_ISREG(inode->i_mode)) {
iput(inode);
if (!d_is_reg(path.dentry)) {
path_put(&path);
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);