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    Subject[PATCH 5.18 039/879] x86/kexec: fix memory leak of elf header buffer
    Date
    From: Baoquan He <bhe@redhat.com>

    commit b3e34a47f98974d0844444c5121aaff123004e57 upstream.

    This is reported by kmemleak detector:

    unreferenced object 0xffffc900002a9000 (size 4096):
    comm "kexec", pid 14950, jiffies 4295110793 (age 373.951s)
    hex dump (first 32 bytes):
    7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 .ELF............
    04 00 3e 00 01 00 00 00 00 00 00 00 00 00 00 00 ..>.............
    backtrace:
    [<0000000016a8ef9f>] __vmalloc_node_range+0x101/0x170
    [<000000002b66b6c0>] __vmalloc_node+0xb4/0x160
    [<00000000ad40107d>] crash_prepare_elf64_headers+0x8e/0xcd0
    [<0000000019afff23>] crash_load_segments+0x260/0x470
    [<0000000019ebe95c>] bzImage64_load+0x814/0xad0
    [<0000000093e16b05>] arch_kexec_kernel_image_load+0x1be/0x2a0
    [<000000009ef2fc88>] kimage_file_alloc_init+0x2ec/0x5a0
    [<0000000038f5a97a>] __do_sys_kexec_file_load+0x28d/0x530
    [<0000000087c19992>] do_syscall_64+0x3b/0x90
    [<0000000066e063a4>] entry_SYSCALL_64_after_hwframe+0x44/0xae

    In crash_prepare_elf64_headers(), a buffer is allocated via vmalloc() to
    store elf headers. While it's not freed back to system correctly when
    kdump kernel is reloaded or unloaded. Then memory leak is caused. Fix it
    by introducing x86 specific function arch_kimage_file_post_load_cleanup(),
    and freeing the buffer there.

    And also remove the incorrect elf header buffer freeing code. Before
    calling arch specific kexec_file loading function, the image instance has
    been initialized. So 'image->elf_headers' must be NULL. It doesn't make
    sense to free the elf header buffer in the place.

    Three different people have reported three bugs about the memory leak on
    x86_64 inside Redhat.

    Link: https://lkml.kernel.org/r/20220223113225.63106-2-bhe@redhat.com
    Signed-off-by: Baoquan He <bhe@redhat.com>
    Acked-by: Dave Young <dyoung@redhat.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kernel/machine_kexec_64.c | 12 +++++++++---
    1 file changed, 9 insertions(+), 3 deletions(-)

    --- a/arch/x86/kernel/machine_kexec_64.c
    +++ b/arch/x86/kernel/machine_kexec_64.c
    @@ -376,9 +376,6 @@ void machine_kexec(struct kimage *image)
    #ifdef CONFIG_KEXEC_FILE
    void *arch_kexec_kernel_image_load(struct kimage *image)
    {
    - vfree(image->elf_headers);
    - image->elf_headers = NULL;
    -
    if (!image->fops || !image->fops->load)
    return ERR_PTR(-ENOEXEC);

    @@ -514,6 +511,15 @@ overflow:
    (int)ELF64_R_TYPE(rel[i].r_info), value);
    return -ENOEXEC;
    }
    +
    +int arch_kimage_file_post_load_cleanup(struct kimage *image)
    +{
    + vfree(image->elf_headers);
    + image->elf_headers = NULL;
    + image->elf_headers_sz = 0;
    +
    + return kexec_image_post_load_cleanup_default(image);
    +}
    #endif /* CONFIG_KEXEC_FILE */

    static int

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