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| author | Zhang Yi <yi.zhang@huawei.com> | 2022-03-01 14:17:04 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2022-03-03 07:56:41 +0300 |
| commit | 5c93e8ecd5bd3bfdee013b6da0850357eb6ca4d8 (patch) | |
| tree | 59493b2132ac471877eb0a7d40128d3b03e040b7 /fs/ext4 | |
| parent | fd9b6fad667c7516a130cf0f3caddcb965710c12 (diff) | |
| download | linux-5c93e8ecd5bd3bfdee013b6da0850357eb6ca4d8.tar.xz | |
ext4: fix underflow in ext4_max_bitmap_size()
when ext4 filesystem is created with 64k block size, ^extent and
^huge_file features. the upper_limit would underflow during the
computations in ext4_max_bitmap_size(). The problem is the size of block
index tree for such large block size is more than i_blocks can carry.
So fix the computation to count with this possibility. After this fix,
the 'res' cannot overflow loff_t on the extreme case of filesystem with
huge_files and 64K block size, so this patch also revert commit
75ca6ad408f4 ("ext4: fix loff_t overflow in ext4_max_bitmap_size()").
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220301111704.2153829-1-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
| -rw-r--r-- | fs/ext4/super.c | 46 |
1 files changed, 31 insertions, 15 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 1fe91a26b88c..1e5f4994fe57 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3481,8 +3481,9 @@ static loff_t ext4_max_size(int blkbits, int has_huge_files) */ static loff_t ext4_max_bitmap_size(int bits, int has_huge_files) { - unsigned long long upper_limit, res = EXT4_NDIR_BLOCKS; + loff_t upper_limit, res = EXT4_NDIR_BLOCKS; int meta_blocks; + unsigned int ppb = 1 << (bits - 2); /* * This is calculated to be the largest file size for a dense, block @@ -3514,27 +3515,42 @@ static loff_t ext4_max_bitmap_size(int bits, int has_huge_files) } + /* Compute how many blocks we can address by block tree */ + res += ppb; + res += ppb * ppb; + res += ((loff_t)ppb) * ppb * ppb; + /* Compute how many metadata blocks are needed */ + meta_blocks = 1; + meta_blocks += 1 + ppb; + meta_blocks += 1 + ppb + ppb * ppb; + /* Does block tree limit file size? */ + if (res + meta_blocks <= upper_limit) + goto check_lfs; + + res = upper_limit; + /* How many metadata blocks are needed for addressing upper_limit? */ + upper_limit -= EXT4_NDIR_BLOCKS; /* indirect blocks */ meta_blocks = 1; + upper_limit -= ppb; /* double indirect blocks */ - meta_blocks += 1 + (1LL << (bits-2)); - /* tripple indirect blocks */ - meta_blocks += 1 + (1LL << (bits-2)) + (1LL << (2*(bits-2))); - - upper_limit -= meta_blocks; - upper_limit <<= bits; - - res += 1LL << (bits-2); - res += 1LL << (2*(bits-2)); - res += 1LL << (3*(bits-2)); + if (upper_limit < ppb * ppb) { + meta_blocks += 1 + DIV_ROUND_UP_ULL(upper_limit, ppb); + res -= meta_blocks; + goto check_lfs; + } + meta_blocks += 1 + ppb; + upper_limit -= ppb * ppb; + /* tripple indirect blocks for the rest */ + meta_blocks += 1 + DIV_ROUND_UP_ULL(upper_limit, ppb) + + DIV_ROUND_UP_ULL(upper_limit, ppb*ppb); + res -= meta_blocks; +check_lfs: res <<= bits; - if (res > upper_limit) - res = upper_limit; - if (res > MAX_LFS_FILESIZE) res = MAX_LFS_FILESIZE; - return (loff_t)res; + return res; } static ext4_fsblk_t descriptor_loc(struct super_block *sb, |