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perf/core: Fix bad use of igrab()

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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 the issue in kernel/event/core.c.

Reviewed-and-tested-by: Alexander Shishkin <[email protected]>
Reported-by: Miklos Szeredi <[email protected]>
Signed-off-by: Song Liu <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Fixes: 375637bc52 ("perf/core: Introduce address range filtering")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Song Liu 2018-04-17 23:29:07 -07:00 • committed by Ingo Molnar
commit 9511bce9fe
3 changed files with 12 additions and 15 deletions
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21
kernel/events/core.c
View file

@ -6668,7 +6668,7 @@ static void perf_event_addr_filters_exec(struct perf_event *event, void *data)
raw_spin_lock_irqsave(&ifh->lock, flags);
list_for_each_entry(filter, &ifh->list, entry) {
if (filter->inode) {
if (filter->path.dentry) {
event->addr_filters_offs[count] = 0;
restart++;
}
@ -7333,7 +7333,7 @@ static bool perf_addr_filter_match(struct perf_addr_filter *filter,
struct file *file, unsigned long offset,
unsigned long size)
{
if (filter->inode != file_inode(file))
if (d_inode(filter->path.dentry) != file_inode(file))
return false;
if (filter->offset > offset + size)
@ -8686,8 +8686,7 @@ static void free_filters_list(struct list_head *filters)
struct perf_addr_filter *filter, *iter;
list_for_each_entry_safe(filter, iter, filters, entry) {
if (filter->inode)
iput(filter->inode);
path_put(&filter->path);
list_del(&filter->entry);
kfree(filter);
}
@ -8784,7 +8783,7 @@ static void perf_event_addr_filters_apply(struct perf_event *event)
* Adjust base offset if the filter is associated to a binary
* that needs to be mapped:
*/
if (filter->inode)
if (filter->path.dentry)
event->addr_filters_offs[count] =
perf_addr_filter_apply(filter, mm);
@ -8858,7 +8857,6 @@ perf_event_parse_addr_filter(struct perf_event *event, char *fstr,
{
struct perf_addr_filter *filter = NULL;
char *start, *orig, *filename = NULL;
struct path path;
substring_t args[MAX_OPT_ARGS];
int state = IF_STATE_ACTION, token;
unsigned int kernel = 0;
@ -8971,19 +8969,18 @@ perf_event_parse_addr_filter(struct perf_event *event, char *fstr,
goto fail_free_name;
/* look up the path and grab its inode */
ret = kern_path(filename, LOOKUP_FOLLOW, &path);
ret = kern_path(filename, LOOKUP_FOLLOW,
&filter->path);
if (ret)
goto fail_free_name;
filter->inode = igrab(d_inode(path.dentry));
path_put(&path);
kfree(filename);
filename = NULL;
ret = -EINVAL;
if (!filter->inode ||
!S_ISREG(filter->inode->i_mode))
/* free_filters_list() will iput() */
if (!filter->path.dentry ||
!S_ISREG(d_inode(filter->path.dentry)
->i_mode))
goto fail;
event->addr_filters.nr_file_filters++;