From 0367e7d1b9bac3a78608a672bf6e4ace6a28b964 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] linux: Fix integer overflows in initrd size handling
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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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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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.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 4cd8c20c7..3fe390f17 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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@@ -4,6 +4,7 @@
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#include <grub/misc.h>
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#include <grub/file.h>
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#include <grub/mm.h>
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+#include <grub/safemath.h>
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struct newc_head
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{
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@@ -98,13 +99,13 @@ 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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@@ -130,14 +131,22 @@ 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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@@ -172,26 +181,33 @@ grub_initrd_init (int argc, char *argv[],
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eptr = grub_strchr (ptr, ':');
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if (eptr)
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{
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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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@@ -207,19 +223,29 @@ 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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@@ -260,8 +286,16 @@ 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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