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    Subject[PATCH 4.14 053/165] x86/kexec: Avoid double free_page() upon do_kexec_load() failure
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

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

    commit a466ef76b815b86748d9870ef2a430af7b39c710 upstream.

    >From ff82bedd3e12f0d3353282054ae48c3bd8c72012 Mon Sep 17 00:00:00 2001
    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Date: Wed, 9 May 2018 12:12:39 +0900
    Subject: [PATCH 4.14 053/165] 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@syzkaller.appspotmail.com>
    Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Acked-by: Baoquan He <bhe@redhat.com>
    Cc: thomas.lendacky@amd.com
    Cc: prudo@linux.vnet.ibm.com
    Cc: Huang Ying <ying.huang@intel.com>
    Cc: syzkaller-bugs@googlegroups.com
    Cc: takahiro.akashi@linaro.org
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: akpm@linux-foundation.org
    Cc: dyoung@redhat.com
    Cc: kirill.shutemov@linux.intel.com
    Link: https://lkml.kernel.org/r/201805091942.DGG12448.tMFVFSJFQOOLHO@I-love.SAKURA.ne.jp
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kernel/machine_kexec_32.c | 6 +++++-
    arch/x86/kernel/machine_kexec_64.c | 5 ++++-
    2 files changed, 9 insertions(+), 2 deletions(-)

    --- 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_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
    @@ -38,9 +38,13 @@ static struct kexec_file_ops *kexec_file
    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)
    @@ -90,7 +94,6 @@ static int init_transition_pgtable(struc
    set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC_NOENC));
    return 0;
    err:
    - free_transition_pgtable(image);
    return result;
    }


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