From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>

Date: Wed, 6 Apr 2022 18:49:09 +0530

Subject: [PATCH] fs/f2fs: Do not read past the end of nat bitmap

A corrupt f2fs filesystem could have a block offset or a bitmap

offset that would cause us to read beyond the bounds of the nat

bitmap.

Introduce the nat_bitmap_size member in grub_f2fs_data which holds

the size of nat bitmap.

Set the size when loading the nat bitmap in nat_bitmap_ptr(), and

catch when an invalid offset would create a pointer past the end of

the allocated space.

Check against the bitmap size in grub_f2fs_test_bit() test bit to avoid

reading past the end of the nat bitmap.

Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>

Signed-off-by: Daniel Axtens <dja@axtens.net>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

(cherry picked from commit 62d63d5e38c67a6e349148bf7cb87c560e935a7e)

---

 grub-core/fs/f2fs.c | 33 +++++++++++++++++++++++++++------

 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/grub-core/fs/f2fs.c b/grub-core/fs/f2fs.c

index 63702214b0..8898b235e0 100644

--- a/grub-core/fs/f2fs.c

+++ b/grub-core/fs/f2fs.c

@@ -122,6 +122,7 @@ GRUB_MOD_LICENSE ("GPLv3+");

 #define F2FS_INLINE_DOTS          0x10  /* File having implicit dot dentries. */

 #define MAX_VOLUME_NAME           512

+#define MAX_NAT_BITMAP_SIZE       3900

 enum FILE_TYPE

 {

@@ -183,7 +184,7 @@ struct grub_f2fs_checkpoint

   grub_uint32_t                   checksum_offset;

   grub_uint64_t                   elapsed_time;

   grub_uint8_t                    alloc_type[MAX_ACTIVE_LOGS];

-  grub_uint8_t                    sit_nat_version_bitmap[3900];

+  grub_uint8_t                    sit_nat_version_bitmap[MAX_NAT_BITMAP_SIZE];

   grub_uint32_t                   checksum;

 } GRUB_PACKED;

@@ -302,6 +303,7 @@ struct grub_f2fs_data

   struct grub_f2fs_nat_journal    nat_j;

   char                            *nat_bitmap;

+  grub_uint32_t                   nat_bitmap_size;

   grub_disk_t                     disk;

   struct grub_f2fs_node           *inode;

@@ -377,15 +379,20 @@ sum_blk_addr (struct grub_f2fs_data *data, int base, int type)

 }

 static void *

-nat_bitmap_ptr (struct grub_f2fs_data *data)

+nat_bitmap_ptr (struct grub_f2fs_data *data, grub_uint32_t *nat_bitmap_size)

 {

   struct grub_f2fs_checkpoint *ckpt = &data->ckpt;

   grub_uint32_t offset;

+  *nat_bitmap_size = MAX_NAT_BITMAP_SIZE;

   if (grub_le_to_cpu32 (data->sblock.cp_payload) > 0)

     return ckpt->sit_nat_version_bitmap;

   offset = grub_le_to_cpu32 (ckpt->sit_ver_bitmap_bytesize);

+  if (offset >= MAX_NAT_BITMAP_SIZE)

+     return NULL;

+

+  *nat_bitmap_size = *nat_bitmap_size - offset;

   return ckpt->sit_nat_version_bitmap + offset;

 }

@@ -438,11 +445,15 @@ grub_f2fs_crc_valid (grub_uint32_t blk_crc, void *buf, const grub_uint32_t len)

 }

 static int

-grub_f2fs_test_bit (grub_uint32_t nr, const char *p)

+grub_f2fs_test_bit (grub_uint32_t nr, const char *p, grub_uint32_t len)

 {

   int mask;

+  grub_uint32_t shifted_nr = (nr >> 3);

-  p += (nr >> 3);

+  if (shifted_nr >= len)

+    return -1;

+

+  p += shifted_nr;

   mask = 1 << (7 - (nr & 0x07));

   return mask & *p;

@@ -662,6 +673,7 @@ get_node_blkaddr (struct grub_f2fs_data *data, grub_uint32_t nid)

   grub_uint32_t seg_off, block_off, entry_off, block_addr;

   grub_uint32_t blkaddr = 0;

   grub_err_t err;

+  int result_bit;

   err = get_blkaddr_from_nat_journal (data, nid, &blkaddr);

   if (err != GRUB_ERR_NONE)

@@ -682,8 +694,15 @@ get_node_blkaddr (struct grub_f2fs_data *data, grub_uint32_t nid)

         ((seg_off * data->blocks_per_seg) << 1) +

         (block_off & (data->blocks_per_seg - 1));

-  if (grub_f2fs_test_bit (block_off, data->nat_bitmap))

+  result_bit = grub_f2fs_test_bit (block_off, data->nat_bitmap,

+                                   data->nat_bitmap_size);

+  if (result_bit > 0)

     block_addr += data->blocks_per_seg;

+  else if (result_bit == -1)

+    {

+      grub_free (nat_block);

+      return 0;

+    }

   err = grub_f2fs_block_read (data, block_addr, nat_block);

   if (err)

@@ -833,7 +852,9 @@ grub_f2fs_mount (grub_disk_t disk)

   if (err)

     goto fail;

-  data->nat_bitmap = nat_bitmap_ptr (data);

+  data->nat_bitmap = nat_bitmap_ptr (data, &data->nat_bitmap_size);

+  if (data->nat_bitmap == NULL)

+    goto fail;

   err = get_nat_journal (data);

   if (err)