Blame SOURCES/0535-fs-f2fs-Do-not-read-past-the-end-of-nat-bitmap.patch

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
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Date: Wed, 6 Apr 2022 18:49:09 +0530
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Subject: [PATCH] fs/f2fs: Do not read past the end of nat bitmap
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A corrupt f2fs filesystem could have a block offset or a bitmap
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offset that would cause us to read beyond the bounds of the nat
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bitmap.
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Introduce the nat_bitmap_size member in grub_f2fs_data which holds
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the size of nat bitmap.
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Set the size when loading the nat bitmap in nat_bitmap_ptr(), and
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catch when an invalid offset would create a pointer past the end of
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the allocated space.
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Check against the bitmap size in grub_f2fs_test_bit() test bit to avoid
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reading past the end of the nat bitmap.
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Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit 62d63d5e38c67a6e349148bf7cb87c560e935a7e)
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(cherry picked from commit 92219e6d379b5b4d30b05361830b72ab1d95d281)
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(cherry picked from commit c23d97e3b56594bf0f802d94062e14b221143115)
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---
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 grub-core/fs/f2fs.c | 33 +++++++++++++++++++++++++++------
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 1 file changed, 27 insertions(+), 6 deletions(-)
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diff --git a/grub-core/fs/f2fs.c b/grub-core/fs/f2fs.c
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index 09dc932420..33e565b180 100644
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--- a/grub-core/fs/f2fs.c
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+++ b/grub-core/fs/f2fs.c
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@@ -122,6 +122,7 @@ GRUB_MOD_LICENSE ("GPLv3+");
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 #define F2FS_INLINE_DOTS          0x10  /* File having implicit dot dentries. */
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 #define MAX_VOLUME_NAME           512
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+#define MAX_NAT_BITMAP_SIZE       3900
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 enum FILE_TYPE
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 {
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@@ -183,7 +184,7 @@ struct grub_f2fs_checkpoint
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   grub_uint32_t                   checksum_offset;
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   grub_uint64_t                   elapsed_time;
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   grub_uint8_t                    alloc_type[MAX_ACTIVE_LOGS];
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-  grub_uint8_t                    sit_nat_version_bitmap[3900];
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+  grub_uint8_t                    sit_nat_version_bitmap[MAX_NAT_BITMAP_SIZE];
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   grub_uint32_t                   checksum;
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 } GRUB_PACKED;
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@@ -302,6 +303,7 @@ struct grub_f2fs_data
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   struct grub_f2fs_nat_journal    nat_j;
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   char                            *nat_bitmap;
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+  grub_uint32_t                   nat_bitmap_size;
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   grub_disk_t                     disk;
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   struct grub_f2fs_node           *inode;
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@@ -377,15 +379,20 @@ sum_blk_addr (struct grub_f2fs_data *data, int base, int type)
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 }
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 static void *
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-nat_bitmap_ptr (struct grub_f2fs_data *data)
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+nat_bitmap_ptr (struct grub_f2fs_data *data, grub_uint32_t *nat_bitmap_size)
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 {
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   struct grub_f2fs_checkpoint *ckpt = &data->ckpt;
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   grub_uint32_t offset;
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+  *nat_bitmap_size = MAX_NAT_BITMAP_SIZE;
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   if (grub_le_to_cpu32 (data->sblock.cp_payload) > 0)
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     return ckpt->sit_nat_version_bitmap;
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   offset = grub_le_to_cpu32 (ckpt->sit_ver_bitmap_bytesize);
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+  if (offset >= MAX_NAT_BITMAP_SIZE)
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+     return NULL;
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+
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+  *nat_bitmap_size = *nat_bitmap_size - offset;
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   return ckpt->sit_nat_version_bitmap + offset;
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 }
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@@ -438,11 +445,15 @@ grub_f2fs_crc_valid (grub_uint32_t blk_crc, void *buf, const grub_uint32_t len)
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 }
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 static int
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-grub_f2fs_test_bit (grub_uint32_t nr, const char *p)
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+grub_f2fs_test_bit (grub_uint32_t nr, const char *p, grub_uint32_t len)
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 {
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   int mask;
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+  grub_uint32_t shifted_nr = (nr >> 3);
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-  p += (nr >> 3);
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+  if (shifted_nr >= len)
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+    return -1;
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+
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+  p += shifted_nr;
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   mask = 1 << (7 - (nr & 0x07));
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   return mask & *p;
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@@ -662,6 +673,7 @@ get_node_blkaddr (struct grub_f2fs_data *data, grub_uint32_t nid)
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   grub_uint32_t seg_off, block_off, entry_off, block_addr;
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   grub_uint32_t blkaddr = 0;
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   grub_err_t err;
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+  int result_bit;
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   err = get_blkaddr_from_nat_journal (data, nid, &blkaddr);
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   if (err != GRUB_ERR_NONE)
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@@ -682,8 +694,15 @@ get_node_blkaddr (struct grub_f2fs_data *data, grub_uint32_t nid)
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         ((seg_off * data->blocks_per_seg) << 1) +
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         (block_off & (data->blocks_per_seg - 1));
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-  if (grub_f2fs_test_bit (block_off, data->nat_bitmap))
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+  result_bit = grub_f2fs_test_bit (block_off, data->nat_bitmap,
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+                                   data->nat_bitmap_size);
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+  if (result_bit > 0)
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     block_addr += data->blocks_per_seg;
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+  else if (result_bit == -1)
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+    {
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+      grub_free (nat_block);
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+      return 0;
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+    }
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   err = grub_f2fs_block_read (data, block_addr, nat_block);
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   if (err)
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@@ -832,7 +851,9 @@ grub_f2fs_mount (grub_disk_t disk)
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   if (err)
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     goto fail;
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-  data->nat_bitmap = nat_bitmap_ptr (data);
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+  data->nat_bitmap = nat_bitmap_ptr (data, &data->nat_bitmap_size);
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+  if (data->nat_bitmap == NULL)
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+    goto fail;
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   err = get_nat_journal (data);
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   if (err)