linux-kernel - [PATCH v4] kernfs: fix memory leak of kernfs_iattrs in __kernfs_new

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Message-Id: <20251125151332.2010687-1-whrosenb@asu.edu>
Date: Tue, 25 Nov 2025 08:13:32 -0700
From: Will Rosenberg <whrosenb@....edu>
To: 
Cc: Will Rosenberg <whrosenb@....edu>,
	Oliver Rosenberg <olrose55@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>,
	Paul Moore <paul@...l-moore.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Ondrej Mosnacek <omosnace@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v4] kernfs: fix memory leak of kernfs_iattrs in __kernfs_new_node

There exists a memory leak of kernfs_iattrs contained as an element
of kernfs_node allocated in __kernfs_new_node(). __kernfs_setattr()
allocates kernfs_iattrs as a sub-object, and the LSM security check
incorrectly errors out and does not free the kernfs_iattrs sub-object.

Make an additional error out case that properly frees kernfs_iattrs if
security_kernfs_init_security() fails.

Fixes: e19dfdc83b60 ("kernfs: initialize security of newly created nodes")
Co-developed-by: Oliver Rosenberg <olrose55@...il.com>
Signed-off-by: Oliver Rosenberg <olrose55@...il.com>
Signed-off-by: Will Rosenberg <whrosenb@....edu>
---

Notes:
    V1 -> V2: meant as a RESEND, but the commit message and notes were also made more succinct. Patch remained unchanged. v1 was not sent to LKML by mistake.
    V2 -> V3: Update Fixes tag in commit message. Patch remains unchanged.
    V3 -> V4: Use kmem_cache_free() in place of kfree(). To be safe and consistent, call simple_xattrs_free() in case simple_xattr is allocated in the future.

 fs/kernfs/dir.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a670ba3e565e..5c0efd6b239f 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -675,11 +675,14 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	if (parent) {
 		ret = security_kernfs_init_security(parent, kn);
 		if (ret)
-			goto err_out3;
+			goto err_out4;
 	}
 
 	return kn;
 
+ err_out4:
+	simple_xattrs_free(&kn->iattr->xattrs, NULL);
+	kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
  err_out3:
 	spin_lock(&root->kernfs_idr_lock);
 	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));

base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa
-- 
2.34.1