On 05/09/18 at 07:42pm, Tetsuo Handa wrote: > >From ff82bedd3e12f0d3353282054ae48c3bd8c72012 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa <[email protected]> > Date: Wed, 9 May 2018 12:12:39 +0900 > Subject: [PATCH v3] 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 > > Signed-off-by: Tetsuo Handa <[email protected]> > Reported-by: syzbot <[email protected]> > 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 <[email protected]> > Cc: H. Peter Anvin <[email protected]> > Cc: Ingo Molnar <[email protected]> > --- > arch/x86/kernel/machine_kexec_32.c | 6 +++++- > arch/x86/kernel/machine_kexec_64.c | 5 ++++- > 2 files changed, 9 insertions(+), 2 deletions(-)
Looks good to me, thx! Acked-by: Baoquan He <[email protected]> Thanks Baoquan > > diff --git a/arch/x86/kernel/machine_kexec_32.c > b/arch/x86/kernel/machine_kexec_32.c > index 60cdec6..d1ab07e 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) > @@ -79,7 +84,6 @@ static int machine_kexec_alloc_page_tables(struct kimage > *image) > !image->arch.pmd0 || !image->arch.pmd1 || > #endif > !image->arch.pte0 || !image->arch.pte1) { > - machine_kexec_free_page_tables(image); > return -ENOMEM; > } > return 0; > diff --git a/arch/x86/kernel/machine_kexec_64.c > b/arch/x86/kernel/machine_kexec_64.c > index a5e55d8..6010449 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) > @@ -91,7 +95,6 @@ static int init_transition_pgtable(struct kimage *image, > pgd_t *pgd) > set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC_NOENC)); > return 0; > err: > - free_transition_pgtable(image); > return result; > } > > -- > 1.8.3.1
