Re: [BUG] x86/sgx: missing kref_put() in sgx_encl_mm_add() error path

[Jarkko Sakkinen <jarkko@kernel.org>]

On Mon, Mar 30, 2026 at 05:09:57PM -0400, Dingisoul wrote:
> Hi Kernel maintainers,
> 
> We found a possible refcount leak in sgx_encl_mm_add().
> 
> In this function, a reference to encl->refcount is taken before registering the MMU notifier:
> 
> /* Grab a refcount for the encl_mm->encl reference: */
> kref_get(&encl->refcount);  // 1. Reference acquired here.
> encl_mm->encl = encl;
> 
> ret = __mmu_notifier_register(&encl_mm->mmu_notifier, mm);
> if (ret) {
> 	kfree(encl_mm);     
> 	return ret;         // 2. Returns without kref_put.
> }
> 
> If __mmu_notifier_register() fails, the function frees encl_mm but does not drop the reference acquired by kref_get(&encl->refcount). This seems to leak one reference to encl.
> 
> Please let us know if the kref_put is unnecessary here.
> 
> Thanks.

It is a leak as encl's, stored in file, will retain increased refcount.

BR, Jarkko