[PATCH v3 7/8] debugfs: call debugfs_real_fops() only after debugfs_file_get()

Nicolai Stange
2017-10-30T23:15:53Z

The current implementation of debugfs_real_fops() relies on a
debugfs_fsdata instance to be installed at ->d_fsdata.

With future patches introducing lazy allocation of these, this requirement
will be guaranteed to be fullfilled only inbetween a
debugfs_file_get()/debugfs_file_put() pair.

The full proxies' fops implemented by debugfs happen to be the only
offenders. Fix them up by moving their debugfs_real_fops() calls past those
to debugfs_file_get().

full_proxy_release() is special as it doesn't invoke debugfs_file_get() at
all. Leave it alone for now.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---
fs/debugfs/file.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 53f5c9a2af88..bc3549c95574 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -144,13 +144,13 @@ const struct file_operations debugfs_open_proxy_file_operations = {
static ret_type full_proxy_ ## name(proto) \
{ \
struct dentry *dentry = F_DENTRY(filp); \
- const struct file_operations *real_fops = \
- debugfs_real_fops(filp); \
+ const struct file_operations *real_fops; \
ret_type r; \
\
r = debugfs_file_get(dentry); \
if (unlikely(r)) \
return r; \
+ real_fops = debugfs_real_fops(filp); \
r = real_fops->name(args); \
debugfs_file_put(dentry); \
return r; \
@@ -177,13 +177,14 @@ FULL_PROXY_FUNC(unlocked_ioctl, long, filp,
static unsigned int full_proxy_poll(struct file *filp,
struct poll_table_struct *wait)
{
- const struct file_operations *real_fops = debugfs_real_fops(filp);
struct dentry *dentry = F_DENTRY(filp);
unsigned int r = 0;
+ const struct file_operations *real_fops;

if (debugfs_file_get(dentry))
return POLLHUP;

+ real_fops = debugfs_real_fops(filp);
r = real_fops->poll(filp, wait);
debugfs_file_put(dentry);
return r;
--
2.13.6