On Wed, Mar 10, 2021 at 07:49:29AM -0800, Sean Christopherson wrote:
On Wed, Mar 10, 2021, Jarkko Sakkinen wrote:
On Wed, Mar 03, 2021 at 08:56:52AM -0800, Dave Hansen wrote:
On 3/3/21 7:03 AM, Jarkko Sakkinen wrote:
If sgx_page_cache_init() fails in the middle, a trivial return statement causes unused memory and virtual address space reserved for the EPC section, not freed. Fix this by using the same rollback, as when sgx_page_reclaimer_init() fails.
...
@@ -708,8 +708,10 @@ static int __init sgx_init(void) if (!cpu_feature_enabled(X86_FEATURE_SGX)) return -ENODEV;
- if (!sgx_page_cache_init())
return -ENOMEM;
- if (!sgx_page_cache_init()) {
ret = -ENOMEM;goto err_page_cache;- }
Currently, the only way sgx_page_cache_init() can fail is in the case that there are no sections:
if (!sgx_nr_epc_sections) { pr_err("There are zero EPC sections.\n"); return false; }That only happened if all sgx_setup_epc_section() calls failed. sgx_setup_epc_section() never both allocates memory with vmalloc for section->pages *and* fails. If sgx_setup_epc_section() has a successful memremap() but a failed vmalloc(), it cleans up with memunmap().
In other words, I see how this _looks_ like a memory leak from sgx_init(), but I don't see an actual leak in practice.
Am I missing something?
In sgx_setup_epc_section():
section->pages = vmalloc(nr_pages * sizeof(struct sgx_epc_page)); if (!section->pages) { memunmap(section->virt_addr); return false; }
I.e. this rollback does not happen without this fix applied:
for (i = 0; i < sgx_nr_epc_sections; i++) { vfree(sgx_epc_sections[i].pages); memunmap(sgx_epc_sections[i].virt_addr); }
Dave is pointing out that sgx_page_cache_init() fails if and only if _all_ sections fail sgx_setup_epc_section(), and if all sections fail then sgx_nr_epc_sections is '0' and the above is a nop.
That behavior is by design, as we didn't want to kill SGX if a single section failed to initialize for whatever reason.
My bad. You're correct. I got mixed up by the rollback :-) Thanks!
I'll just drop the whole patch.
/Jarkko