>From d54b2acf63191eba3d5052bf34fe6d26e3580ac2 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Date: Tue, 1 May 2018 15:36:52 +0900 Subject: [PATCH] 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 explicitly setting NULL after free_page(). [1] https://syzkaller.appspot.com/bug?id=91e52396168cf2bdd572fe1e1bc0bc645c1c6b40 Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Reported-by: syzbot <syzbot+d96f60296ef613fe1...@syzkaller.appspotmail.com> Fixes: f5deb79679af6eb4 ("x86: kexec: Use one page table in x86_64 machine_kexec") Fixes: 92be3d6bdf2cb349 ("kexec/i386: allocate page table pages dynamically") Cc: Huang Ying <ying.hu...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Ingo Molnar <mi...@elte.hu> --- arch/x86/kernel/machine_kexec_32.c | 5 +++++ arch/x86/kernel/machine_kexec_64.c | 4 ++++ 2 files changed, 9 insertions(+) diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c index 60cdec6..ceccfe4 100644 --- a/arch/x86/kernel/machine_kexec_32.c +++ b/arch/x86/kernel/machine_kexec_32.c @@ -57,12 +57,17 @@ 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) diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index a5e55d8..76aaee9 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -39,9 +39,13 @@ static void free_transition_pgtable(struct kimage *image) { free_page((unsigned long)image->arch.p4d); + image->arch.p4d = NULL; 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) -- 1.8.3.1
