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| author | Jan Kara <jack@suse.cz> | 2019-01-29 19:17:24 +0300 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2019-01-31 12:59:12 +0300 |
| commit | 1c2d14212b15a60300a2d4f6364753e87394c521 (patch) | |
| tree | 883e0dbdac3a4a99a464d95e325a87bd3f06525a /fs/ext2 | |
| parent | 4bc74ba1c7320933ba8d59a42563b722fe539a36 (diff) | |
| download | linux-1c2d14212b15a60300a2d4f6364753e87394c521.tar.xz | |
ext2: Fix underflow in ext2_max_size()
When ext2 filesystem is created with 64k block size, ext2_max_size()
will return value less than 0. Also, we cannot write any file in this fs
since the sb->maxbytes is less than 0. The core of the problem is that
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.
File size limits computed with the new function for the full range of
possible block sizes look like:
bits file_size
10 17247252480
11 275415851008
12 2196873666560
13 2197948973056
14 2198486220800
15 2198754754560
16 2198888906752
CC: stable@vger.kernel.org
Reported-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/ext2')
| -rw-r--r-- | fs/ext2/super.c | 39 |
1 files changed, 25 insertions, 14 deletions
diff --git a/fs/ext2/super.c b/fs/ext2/super.c index 133012e46155..0128010a0874 100644 --- a/fs/ext2/super.c +++ b/fs/ext2/super.c @@ -757,7 +757,8 @@ static loff_t ext2_max_size(int bits) { loff_t res = EXT2_NDIR_BLOCKS; int meta_blocks; - loff_t upper_limit; + unsigned int upper_limit; + unsigned int ppb = 1 << (bits-2); /* This is calculated to be the largest file size for a * dense, file such that the total number of @@ -771,24 +772,34 @@ static loff_t ext2_max_size(int bits) /* total blocks in file system block size */ upper_limit >>= (bits - 9); + /* Compute how many blocks we can address by block tree */ + res += 1LL << (bits-2); + res += 1LL << (2*(bits-2)); + res += 1LL << (3*(bits-2)); + /* Does block tree limit file size? */ + if (res < upper_limit) + goto check_lfs; + res = upper_limit; + /* How many metadata blocks are needed for addressing upper_limit? */ + upper_limit -= EXT2_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(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(upper_limit, ppb) + + DIV_ROUND_UP(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; |