kexec_file: increase maximum file size to 4G

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.

Link: https://lkml.kernel.org/r/20220527025535.3953665-3-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 145321a5e798a647f299b1728a61231d166621ce..9b2839775c837ba55199fa9c8526fde67b04c8ca 100644 (file)
--- 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    min_t(s64, 4LL << 30, SSIZE_MAX)
+
 /*
  * Currently this is the only default function that is exported as some
  * architectures need it to do additional handlings.
@@ -189,11 +192,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
                             const char __user *cmdline_ptr,
                             unsigned long cmdline_len, unsigned flags)
 {
-       int ret;
+       ssize_t ret;
        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;
@@ -213,7 +217,7 @@ 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;