linux-kernel - Re: [PATCH] kexec_file: Increase maximum file size to 4G

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Date:   Thu, 26 May 2022 16:45:45 -0400
From:   Pasha Tatashin <pasha.tatashin@...een.com>
To:     Pasha Tatashin <pasha.tatashin@...een.com>,
        Sasha Levin <sashal@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        kexec mailing list <kexec@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>, rburanyi@...gle.com,
        Greg Thelen <gthelen@...gle.com>
Subject: Re: [PATCH] kexec_file: Increase maximum file size to 4G

On Thu, May 26, 2022 at 4:38 PM Pasha Tatashin
<pasha.tatashin@...een.com> wrote:
>
> In some case initrd can be large. For example, it could be a netboot
> image loaded by u-root, that is kexec'ing into it.
>
> The maximum size of initrd is arbitrary set to 2G. Also, the limit is
> not very obvious because it is hidden behind a generic INT_MAX macro.
>
> Theoretically, we could make it LONG_MAX, but it is safer to keep it
> sane, and just increase it to 4G.
>
> Increase the size to 4G, and make it obvious by having a new macro
> that specifies the maximum file size supported by kexec_file_load()
> syscall: KEXEC_FILE_SIZE_MAX.
>
> Signed-off-by: Pasha Tatashin <tatashin@...gle.com>

Should be instead:
Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>

Thanks,
Pasha

> ---
>  kernel/kexec_file.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 8347fc158d2b..1be2227b33e6 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -31,6 +31,9 @@
>
>  static int kexec_calculate_store_digests(struct kimage *image);
>
> +/* Maximum size in bytes for kernel/initrd files. */
> +#define KEXEC_FILE_SIZE_MAX    (4UL << 30)
> +
>  /*
>   * Currently this is the only default function that is exported as some
>   * architectures need it to do additional handlings.
> @@ -227,7 +230,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>         void *ldata;
>
>         ret = kernel_read_file_from_fd(kernel_fd, 0, &image->kernel_buf,
> -                                      INT_MAX, NULL, READING_KEXEC_IMAGE);
> +                                      KEXEC_FILE_SIZE_MAX, NULL,
> +                                      READING_KEXEC_IMAGE);
>         if (ret < 0)
>                 return ret;
>         image->kernel_buf_len = ret;
> @@ -247,7 +251,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>         /* It is possible that there no initramfs is being loaded */
>         if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
>                 ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
> -                                              INT_MAX, NULL,
> +                                              KEXEC_FILE_SIZE_MAX, NULL,
>                                                READING_KEXEC_INITRAMFS);
>                 if (ret < 0)
>                         goto out;
> --
> 2.36.1.124.g0e6072fb45-goog
>