linux-kernel - [PATCH 4.4 92/92] x86/kexec: Avoid double free_page() upon do_kexec

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Message-Id: <20180524093207.942887424@linuxfoundation.org>
Date:   Thu, 24 May 2018 11:39:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot <syzbot+d96f60296ef613fe1d69@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Thomas Gleixner <tglx@...utronix.de>,
        Baoquan He <bhe@...hat.com>, thomas.lendacky@....com,
        prudo@...ux.vnet.ibm.com, Huang Ying <ying.huang@...el.com>,
        syzkaller-bugs@...glegroups.com, takahiro.akashi@...aro.org,
        "H. Peter Anvin" <hpa@...or.com>, akpm@...ux-foundation.org,
        dyoung@...hat.com, kirill.shutemov@...ux.intel.com
Subject: [PATCH 4.4 92/92] x86/kexec: Avoid double free_page() upon do_kexec_load() failure

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit a466ef76b815b86748d9870ef2a430af7b39c710 upstream.

>>From ff82bedd3e12f0d3353282054ae48c3bd8c72012 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Wed, 9 May 2018 12:12:39 +0900
Subject: [PATCH 4.4 92/92] x86/kexec: Avoid double free_page() upon do_kexec_load() failure

syzbot is reporting crashes after memory allocation failure inside
do_kexec_load() [1]. This is because free_transition_pgtable() is called
by both init_transition_pgtable() and machine_kexec_cleanup() when memory
allocation failed inside init_transition_pgtable().

Regarding 32bit code, machine_kexec_free_page_tables() is called by both
machine_kexec_alloc_page_tables() and machine_kexec_cleanup() when memory
allocation failed inside machine_kexec_alloc_page_tables().

Fix this by leaving the error handling to machine_kexec_cleanup()
(and optionally setting NULL after free_page()).

[1] https://syzkaller.appspot.com/bug?id=91e52396168cf2bdd572fe1e1bc0bc645c1c6b40

Fixes: f5deb79679af6eb4 ("x86: kexec: Use one page table in x86_64 machine_kexec")
Fixes: 92be3d6bdf2cb349 ("kexec/i386: allocate page table pages dynamically")
Reported-by: syzbot <syzbot+d96f60296ef613fe1d69@...kaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Baoquan He <bhe@...hat.com>
Cc: thomas.lendacky@....com
Cc: prudo@...ux.vnet.ibm.com
Cc: Huang Ying <ying.huang@...el.com>
Cc: syzkaller-bugs@...glegroups.com
Cc: takahiro.akashi@...aro.org
Cc: H. Peter Anvin <hpa@...or.com>
Cc: akpm@...ux-foundation.org
Cc: dyoung@...hat.com
Cc: kirill.shutemov@...ux.intel.com
Link: https://lkml.kernel.org/r/201805091942.DGG12448.tMFVFSJFQOOLHO@I-love.SAKURA.ne.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/machine_kexec_32.c |    6 +++++-
 arch/x86/kernel/machine_kexec_64.c |    4 +++-
 2 files changed, 8 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -71,12 +71,17 @@ static void load_segments(void)
 static void machine_kexec_free_page_tables(struct kimage *image)
 {
 	free_page((unsigned long)image->arch.pgd);
+	image->arch.pgd = NULL;
 #ifdef CONFIG_X86_PAE
 	free_page((unsigned long)image->arch.pmd0);
+	image->arch.pmd0 = NULL;
 	free_page((unsigned long)image->arch.pmd1);
+	image->arch.pmd1 = NULL;
 #endif
 	free_page((unsigned long)image->arch.pte0);
+	image->arch.pte0 = NULL;
 	free_page((unsigned long)image->arch.pte1);
+	image->arch.pte1 = NULL;
 }

 static int machine_kexec_alloc_page_tables(struct kimage *image)
@@ -93,7 +98,6 @@ static int machine_kexec_alloc_page_tabl
 	    !image->arch.pmd0 || !image->arch.pmd1 ||
 #endif
 	    !image->arch.pte0 || !image->arch.pte1) {
-		machine_kexec_free_page_tables(image);
 		return -ENOMEM;
 	}
 	return 0;
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -37,8 +37,11 @@ static struct kexec_file_ops *kexec_file
 static void free_transition_pgtable(struct kimage *image)
 {
 	free_page((unsigned long)image->arch.pud);
+	image->arch.pud = NULL;
 	free_page((unsigned long)image->arch.pmd);
+	image->arch.pmd = NULL;
 	free_page((unsigned long)image->arch.pte);
+	image->arch.pte = NULL;
 }

 static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
@@ -79,7 +82,6 @@ static int init_transition_pgtable(struc
 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
 	return 0;
 err:
-	free_transition_pgtable(image);
 	return result;
 }