Re: Regression on linux-next (next-20250120)

[Al Viro <viro@zeniv.linux.org.uk>]

On Sun, Jan 26, 2025 at 04:54:55PM +0100, Alexander Gordeev wrote:

> > > Since the version next-20250120 [2], we are seeing the following regression
> > 
> > Ugh...  To narrow the things down, could you see if replacing
> >                 fsd = kmalloc(sizeof(*fsd), GFP_KERNEL);
> > with
> >                 fsd = kzalloc(sizeof(*fsd), GFP_KERNEL);
> > in fs/debugfs/file.c:__debugfs_file_get() affects the test?
> 
> This change fixes lots of the below failures in our CI. FWIW:
> 
> Tested-by: Alexander Gordeev <agordeev@linux.ibm.com>

The real fix follows:

[PATCH] Fix the missing initializations in __debugfs_file_get()

both method table pointers in debugfs_fsdata need to be initialized,
obviously...

Fixes: 41a0ecc0997c "debugfs: get rid of dynamically allocation proxy_ops"
Fucked-up-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index e33cc77699cd..212cd8128e1f 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -111,6 +111,7 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 				fsd->methods |= HAS_READ;
 			if (ops->write)
 				fsd->methods |= HAS_WRITE;
+			fsd->real_fops = NULL;
 		} else {
 			const struct file_operations *ops;
 			ops = fsd->real_fops = DEBUGFS_I(inode)->real_fops;
@@ -124,6 +125,7 @@ static int __debugfs_file_get(struct dentry *dentry, enum dbgfs_get_mode mode)
 				fsd->methods |= HAS_IOCTL;
 			if (ops->poll)
 				fsd->methods |= HAS_POLL;
+			fsd->short_fops = NULL;
 		}
 		refcount_set(&fsd->active_users, 1);
 		init_completion(&fsd->active_users_drained);