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authorJan Kara <jack@suse.cz>2019-01-29 19:17:24 +0300
committerJan Kara <jack@suse.cz>2019-01-31 12:59:12 +0300
commit1c2d14212b15a60300a2d4f6364753e87394c521 (patch)
tree883e0dbdac3a4a99a464d95e325a87bd3f06525a /fs/ext2/super.c
parent4bc74ba1c7320933ba8d59a42563b722fe539a36 (diff)
downloadlinux-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/super.c')
-rw-r--r--fs/ext2/super.c39
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;