On 10/29/21 at 03:24pm, Baoquan He wrote:
> 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.
>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
It deserves to add a Fixes tag, and this drawback exists since
kexec_file_load added. It wastes one page of memory, or severa pages
depending on the cpu numbers, not sure if it deserves to cc stable.
Fixes: cb1052581e2b ("kexec: implementation of new syscall kexec_file_load")
> ---
> arch/x86/kernel/machine_kexec_64.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index 131f30fdcfbd..fd8223fa2de5 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -511,6 +511,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
> (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
> --
> 2.17.2
>
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