From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrey Ryabinin , "Kirill A. Shutemov" , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.17 45/46] x86/mm: Dont free P4D table when it is folded at runtime Date: Fri, 6 Jul 2018 07:47:06 +0200 Message-Id: <20180706054526.911333236@linuxfoundation.org> In-Reply-To: <20180706054524.595521988@linuxfoundation.org> References: <20180706054524.595521988@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrey Ryabinin commit 0e311d237d7f3022b7dafb639b42541bfb42fe94 upstream. When the P4D page table layer is folded at runtime, the p4d_free() should do nothing, the same as in . It seems this bug should cause double-free in efi_call_phys_epilog(), but I don't know how to trigger that code path, so I can't confirm that by testing. Signed-off-by: Andrey Ryabinin Reviewed-by: Kirill A. Shutemov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org # 4.17 Fixes: 98219dda2ab5 ("x86/mm: Fold p4d page table layer at runtime") Link: http://lkml.kernel.org/r/20180625102427.15015-1-aryabinin@virtuozzo.com Signed-off-by: Ingo Molnar Signed-off-by: Andrey Ryabinin Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/pgalloc.h | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/include/asm/pgalloc.h +++ b/arch/x86/include/asm/pgalloc.h @@ -184,6 +184,9 @@ static inline p4d_t *p4d_alloc_one(struc static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d) { + if (!pgtable_l5_enabled) + return; + BUG_ON((unsigned long)p4d & (PAGE_SIZE-1)); free_page((unsigned long)p4d); }