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From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
To:     Jarkko Sakkinen <jarkko@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shuah Khan <shuah@kernel.org>, haitao.huang@intel.com,
        Kai Huang <kai.huang@intel.com>, x86@kernel.org,
        linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        Jia Zhang <zhang.jia@linux.alibaba.com>
Cc:     Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Subject: [PATCH] x86/sgx: Fix free_cnt counting logic in epc section
Date:   Mon, 18 Jan 2021 21:33:47 +0800
Message-Id: <20210118133347.99158-1-tianjia.zhang@linux.alibaba.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Increase `section->free_cnt` in sgx_sanitize_section() is
more reasonable, which is called in ksgxd kernel thread,
instead of assigning it to epc section pages number at
initialization. Although this is unlikely to fail, these
pages cannot be allocated after initialization, and which
need to be reset by ksgxd.

Reported-by: Jia Zhang <zhang.jia@linux.alibaba.com>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c519fc5f6948..9e9a3cf7c00b 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -48,9 +48,10 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
 					struct sgx_epc_page, list);
 
 		ret = __eremove(sgx_get_epc_virt_addr(page));
-		if (!ret)
+		if (!ret) {
 			list_move(&page->list, &section->page_list);
-		else
+			section->free_cnt += 1;
+		} else
 			list_move_tail(&page->list, &dirty);
 
 		spin_unlock(&section->lock);
@@ -646,7 +647,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 		list_add_tail(&section->pages[i].list, &section->init_laundry_list);
 	}
 
-	section->free_cnt = nr_pages;
 	return true;
 }
 
-- 
2.19.1.3.ge56e4f7