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Blame SOURCES/0314-linux-Fix-integer-overflows-in-initrd-size-handling.patch

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From 9715e08cf30ebd8a24ca27b7c4dda8e949e100df Mon Sep 17 00:00:00 2001
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From: Colin Watson <cjwatson@debian.org>
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Date: Sat, 25 Jul 2020 12:15:37 +0100
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Subject: [PATCH 314/314] linux: Fix integer overflows in initrd size handling
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These could be triggered by a crafted filesystem with very large files.
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Fixes: CVE-2020-15707
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Signed-off-by: Colin Watson <cjwatson@debian.org>
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Reviewed-by: Jan Setje-Eilers <jan.setjeeilers@oracle.com>
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---
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 grub-core/loader/linux.c | 74 +++++++++++++++++++++++++++++-----------
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 1 file changed, 54 insertions(+), 20 deletions(-)
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diff --git a/grub-core/loader/linux.c b/grub-core/loader/linux.c
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index 61a2e144db0..0953f6d3266 100644
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--- a/grub-core/loader/linux.c
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+++ b/grub-core/loader/linux.c
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@@ -5,6 +5,7 @@
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 #include <grub/file.h>
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 #include <grub/mm.h>
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 #include <grub/tpm.h>
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+#include <grub/safemath.h>
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 struct newc_head
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 {
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@@ -99,13 +100,13 @@ free_dir (struct dir *root)
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   grub_free (root);
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 }
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-static grub_size_t
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+static grub_err_t
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 insert_dir (const char *name, struct dir **root,
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-	    grub_uint8_t *ptr)
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+	    grub_uint8_t *ptr, grub_size_t *size)
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 {
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   struct dir *cur, **head = root;
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   const char *cb, *ce = name;
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-  grub_size_t size = 0;
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+  *size = 0;
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   while (1)
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     {
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       for (cb = ce; *cb == '/'; cb++);
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@@ -131,14 +132,22 @@ insert_dir (const char *name, struct dir **root,
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 	      ptr = make_header (ptr, name, ce - name,
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 				 040777, 0);
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 	    }
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-	  size += ALIGN_UP ((ce - (char *) name)
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-			    + sizeof (struct newc_head), 4);
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+	  if (grub_add (*size,
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+		        ALIGN_UP ((ce - (char *) name)
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+				  + sizeof (struct newc_head), 4),
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+			size))
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+	    {
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+	      grub_error (GRUB_ERR_OUT_OF_RANGE, N_("overflow is detected"));
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+	      grub_free (n->name);
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+	      grub_free (n);
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+	      return grub_errno;
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+	    }
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 	  *head = n;
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 	  cur = n;
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 	}
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       root = &cur->next;
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     }
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-  return size;
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+  return GRUB_ERR_NONE;
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 }
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 grub_err_t
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@@ -175,26 +184,33 @@ grub_initrd_init (int argc, char *argv[],
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 	  if (eptr)
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 	    {
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 	      grub_file_filter_disable_compression ();
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+	      grub_size_t dir_size, name_len;
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+
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 	      initrd_ctx->components[i].newc_name = grub_strndup (ptr, eptr - ptr);
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-	      if (!initrd_ctx->components[i].newc_name)
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+	      if (!initrd_ctx->components[i].newc_name ||
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+		  insert_dir (initrd_ctx->components[i].newc_name, &root, 0,
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+			      &dir_size))
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 		{
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 		  grub_initrd_close (initrd_ctx);
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 		  return grub_errno;
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 		}
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-	      initrd_ctx->size
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-		+= ALIGN_UP (sizeof (struct newc_head)
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-			    + grub_strlen (initrd_ctx->components[i].newc_name),
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-			     4);
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-	      initrd_ctx->size += insert_dir (initrd_ctx->components[i].newc_name,
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-					      &root, 0);
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+	      name_len = grub_strlen (initrd_ctx->components[i].newc_name);
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+	      if (grub_add (initrd_ctx->size,
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+			    ALIGN_UP (sizeof (struct newc_head) + name_len, 4),
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+			    &initrd_ctx->size) ||
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+		  grub_add (initrd_ctx->size, dir_size, &initrd_ctx->size))
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+		goto overflow;
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 	      newc = 1;
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 	      fname = eptr + 1;
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 	    }
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 	}
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       else if (newc)
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 	{
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-	  initrd_ctx->size += ALIGN_UP (sizeof (struct newc_head)
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-					+ sizeof ("TRAILER!!!") - 1, 4);
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+	  if (grub_add (initrd_ctx->size,
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+			ALIGN_UP (sizeof (struct newc_head)
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+				  + sizeof ("TRAILER!!!") - 1, 4),
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+			&initrd_ctx->size))
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+	    goto overflow;
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 	  free_dir (root);
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 	  root = 0;
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 	  newc = 0;
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@@ -209,19 +225,29 @@ grub_initrd_init (int argc, char *argv[],
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       initrd_ctx->nfiles++;
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       initrd_ctx->components[i].size
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 	= grub_file_size (initrd_ctx->components[i].file);
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-      initrd_ctx->size += initrd_ctx->components[i].size;
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+      if (grub_add (initrd_ctx->size, initrd_ctx->components[i].size,
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+		    &initrd_ctx->size))
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+	goto overflow;
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     }
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   if (newc)
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     {
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       initrd_ctx->size = ALIGN_UP (initrd_ctx->size, 4);
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-      initrd_ctx->size += ALIGN_UP (sizeof (struct newc_head)
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-				    + sizeof ("TRAILER!!!") - 1, 4);
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+      if (grub_add (initrd_ctx->size,
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+		    ALIGN_UP (sizeof (struct newc_head)
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+			      + sizeof ("TRAILER!!!") - 1, 4),
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+		    &initrd_ctx->size))
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+	goto overflow;
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       free_dir (root);
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       root = 0;
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     }
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   return GRUB_ERR_NONE;
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+
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+overflow:
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+  free_dir (root);
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+  grub_initrd_close (initrd_ctx);
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+  return grub_error (GRUB_ERR_OUT_OF_RANGE, N_("overflow is detected"));
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 }
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 grub_size_t
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@@ -262,8 +288,16 @@ grub_initrd_load (struct grub_linux_initrd_context *initrd_ctx,
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       if (initrd_ctx->components[i].newc_name)
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 	{
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-	  ptr += insert_dir (initrd_ctx->components[i].newc_name,
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-			     &root, ptr);
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+	  grub_size_t dir_size;
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+
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+	  if (insert_dir (initrd_ctx->components[i].newc_name, &root, ptr,
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+			  &dir_size))
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+	    {
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+	      free_dir (root);
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+	      grub_initrd_close (initrd_ctx);
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+	      return grub_errno;
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+	    }
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+	  ptr += dir_size;
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 	  ptr = make_header (ptr, initrd_ctx->components[i].newc_name,
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 			     grub_strlen (initrd_ctx->components[i].newc_name),
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 			     0100777,
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-- 
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2.26.2
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