[PATCH] commands/linux: verify kernel file size

From: jinkangkang <[email protected]>

we encountered some issues with grub boot failure on Linux systems. Upon
investigation, it was found that the ext4 fs of the system was abnormal,
causing the ext2 module of GRUB to read empty file contents. Therefore,
a verification of file size was added
'''
error: ../../grub-core/loader/i386/pc/linux.c:170:invalid magic number.
error :
../../grub-core/loader/i386/pc/linux.c:418:you need to load the kernel
first

grub> hexdump /boot/vmlinuz-5.10.134-17.2.a18.x86_64
grub>
grub> cat /boot/vmlinuz-5.10.134-17.2 a18 x86_64
grub>
'''
Verifying the file size in advance may make it easier to identify
the true cause of the problem

---
 grub-core/loader/efi/linux.c      | 7 +++++++
 grub-core/loader/i386/efi/linux.c | 7 ++++++-
 grub-core/loader/i386/linux.c     | 8 ++++++++
 grub-core/loader/i386/pc/linux.c  | 6 ++++++
 4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/grub-core/loader/efi/linux.c b/grub-core/loader/efi/linux.c
index 111edf0e1..23f802044 100644
--- a/grub-core/loader/efi/linux.c
+++ b/grub-core/loader/efi/linux.c
@@ -834,6 +834,13 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
     goto fail;
 
   filelen = grub_file_size (file);
+  if (filelen < (grub_off_t) sizeof (lh))
+    {
+      grub_error (GRUB_ERR_BAD_OS, N_("kernel %s size = %x is too small"),
+                  argv[0], (unsigned) filelen);
+      goto fail;
+    }
+
   kernel = grub_malloc(filelen);
   if (!kernel)
     {
diff --git a/grub-core/loader/i386/efi/linux.c b/grub-core/loader/i386/efi/linux.c
index 6c310d987..a578da896 100644
--- a/grub-core/loader/i386/efi/linux.c
+++ b/grub-core/loader/i386/efi/linux.c
@@ -358,7 +358,12 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
     goto fail;
 
   filelen = grub_file_size (file);
-
+  if (filelen < (grub_ssize_t) sizeof (lh))
+    {
+      grub_error (GRUB_ERR_BAD_OS, N_("kernel %s size = %x is too small"),
+                  argv[0], (unsigned) filelen);
+      goto fail;
+    }
   kernel = grub_malloc(filelen);
   if (!kernel)
     {
diff --git a/grub-core/loader/i386/linux.c b/grub-core/loader/i386/linux.c
index 33a852197..68957f1dd 100644
--- a/grub-core/loader/i386/linux.c
+++ b/grub-core/loader/i386/linux.c
@@ -685,6 +685,14 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
     goto fail;
 
   len = grub_file_size (file);
+
+  if (len < (grub_ssize_t) sizeof (lh))
+    {
+      grub_error (GRUB_ERR_BAD_OS, N_("kernel %s size = %x is too small"),
+                  argv[0], (unsigned) len);
+      goto fail;
+    }
+
   kernel = grub_malloc (len);
   if (!kernel)
     {
diff --git a/grub-core/loader/i386/pc/linux.c b/grub-core/loader/i386/pc/linux.c
index 54a76504a..c9811afea 100644
--- a/grub-core/loader/i386/pc/linux.c
+++ b/grub-core/loader/i386/pc/linux.c
@@ -147,6 +147,12 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
     goto fail;
 
   len = grub_file_size (file);
+  if (len < (grub_ssize_t) sizeof (lh))
+    {
+      grub_error (GRUB_ERR_BAD_OS, N_("kernel %s size = %x is too small"),
+                  argv[0], (unsigned) len);
+      goto fail;
+    }
   kernel = grub_malloc (len);
   if (!kernel)
     {
-- 
2.50.1.windows.1


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