From 5ac885d02a9e91a5d6760090f90fa2bb4e7a5dd6 Mon Sep 17 00:00:00 2001 From: Sudhakar Kuppusamy Date: Wed, 6 Apr 2022 18:49:09 +0530 Subject: [PATCH 27/32] 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 Signed-off-by: Daniel Axtens Reviewed-by: Daniel Kiper --- 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); + + if (shifted_nr >= len) + return -1; - p += (nr >> 3); + 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) -- 2.34.1