On Tue, Dec 16, 2025 at 09:43:35AM -0700, Will Rosenberg wrote:

There exists a null pointer dereference in simple_xattrs_free() as part of the __kernfs_new_node() routine. Within __kernfs_new_node(), err_out4 calls simple_xattr_free(), but kn->iattr may be NULL if __kernfs_setattr() was never called. As a result, the first argument to simple_xattrs_free() may be NULL + 0x38, and no NULL check is done internally, causing an incorrect pointer dereference.

Add a check to ensure kn->iattr is not NULL, meaning __kernfs_setattr() has been called and kn->iattr is allocated. Note that struct kernfs_node kn is allocated with kmem_cache_zalloc, so we can assume kn->iattr will be NULL if not allocated.

An alternative fix could be to not call simple_xattr_free() at all. As was previously discussed during the initial patch, simple_xattr_free() is not strictly needed and is included to be consistent with kernfs_free_rcu(), which also helps the function maintain correctness if changes are made in __kernfs_new_node().

Reported-by: syzbot+6aaf7f48ae034ab0ea97@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6aaf7f48ae034ab0ea97 Fixes: 382b1e8f30f7 ("kernfs: fix memory leak of kernfs_iattrs in __kernfs_new_node") Cc: stable@vger.kernel.org Signed-off-by: Will Rosenberg whrosenb@asu.edu

---

fs/kernfs/dir.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 5c0efd6b239f..29baeeb97871 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -681,8 +681,10 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root, return kn; err_out4:

• simple_xattrs_free(&kn->iattr->xattrs, NULL);
• kmem_cache_free(kernfs_iattrs_cache, kn->iattr);

• if (kn->iattr) {

• 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: d358e5254674b70f34c847715ca509e46eb81e6f

2.34.1

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman. You have sent him a patch that has triggered this response. He used to manually respond to these common problems, but in order to save his sanity (he kept writing the same thing over and over, yet to different people), I was created. Hopefully you will not take offence and will fix the problem in your patch and resubmit it so that it can be accepted into the Linux kernel tree.

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