[PATCH] x86/mm/mem_encrypt_identity : fix error useage to sizeof

[PATCH] x86/mm/mem_encrypt_identity : fix error useage to sizeof

[Peng Hao]

Fix error usage to sizeof. It should not use sizeof to pointer.

Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
---
 arch/x86/mm/mem_encrypt_identity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index a19ef1a..4aa9b14 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -158,8 +158,8 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
 	pmd = pmd_offset(pud, ppd->vaddr);
 	if (pmd_none(*pmd)) {
 		pte = ppd->pgtable_area;
-		memset(pte, 0, sizeof(pte) * PTRS_PER_PTE);
-		ppd->pgtable_area += sizeof(pte) * PTRS_PER_PTE;
+		memset(pte, 0, sizeof(*pte) * PTRS_PER_PTE);
+		ppd->pgtable_area += sizeof(*pte) * PTRS_PER_PTE;
 		set_pmd(pmd, __pmd(PMD_FLAGS | __pa(pte)));
 	}
 
-- 
1.8.3.1

Re: [PATCH] x86/mm/mem_encrypt_identity : fix error useage to sizeof

[Borislav Petkov]

On Sat, Dec 29, 2018 at 02:34:12PM +0800, Peng Hao wrote:
> Fix error usage to sizeof. It should not use sizeof to pointer.

... because?

The commit message needs to explain what the potential issue could be
and why it doesn't matter in this case.

Thx.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

[tip:x86/urgent] x86/mm/mem_encrypt: Fix erroneous sizeof()

[tip-bot for Peng Hao]

Commit-ID:  bf7d28c53453ea904584960de55e33e03b9d93b1
Gitweb:     https://git.kernel.org/tip/bf7d28c53453ea904584960de55e33e03b9d93b1
Author:     Peng Hao <peng.hao2@zte.com.cn>
AuthorDate: Sat, 29 Dec 2018 14:34:12 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 15 Jan 2019 11:41:58 +0100

x86/mm/mem_encrypt: Fix erroneous sizeof()

Using sizeof(pointer) for determining the size of a memset() only works
when the size of the pointer and the size of type to which it points are
the same. For pte_t this is only true for 64bit and 32bit-NONPAE. On 32bit
PAE systems this is wrong as the pointer size is 4 byte but the PTE entry
is 8 bytes. It's actually not a real world issue as this code depends on
64bit, but it's wrong nevertheless.

Use sizeof(*p) for correctness sake.

Fixes: aad983913d77 ("x86/mm/encrypt: Simplify sme_populate_pgd() and sme_populate_pgd_large()")
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: dave.hansen@linux.intel.com
Cc: peterz@infradead.org
Cc: luto@kernel.org
Link: https://lkml.kernel.org/r/1546065252-97996-1-git-send-email-peng.hao2@zte.com.cn

---
 arch/x86/mm/mem_encrypt_identity.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index a19ef1a416ff..4aa9b1480866 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -158,8 +158,8 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
 	pmd = pmd_offset(pud, ppd->vaddr);
 	if (pmd_none(*pmd)) {
 		pte = ppd->pgtable_area;
-		memset(pte, 0, sizeof(pte) * PTRS_PER_PTE);
-		ppd->pgtable_area += sizeof(pte) * PTRS_PER_PTE;
+		memset(pte, 0, sizeof(*pte) * PTRS_PER_PTE);
+		ppd->pgtable_area += sizeof(*pte) * PTRS_PER_PTE;
 		set_pmd(pmd, __pmd(PMD_FLAGS | __pa(pte)));
 	}