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ext4: fix loff_t overflow in ext4_max_bitmap_size()

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We should use unsigned long long rather than loff_t to avoid
overflow in ext4_max_bitmap_size() for comparison before returning.
w/o this patch sbi->s_bitmap_maxbytes was becoming a negative
value due to overflow of upper_limit (with has_huge_files as true)

Below is a quick test to trigger it on a 64KB pagesize system.

sudo mkfs.ext4 -b 65536 -O ^has_extents,^64bit /dev/loop2
sudo mount /dev/loop2 /mnt
sudo echo "hello" > /mnt/hello 	-> This will error out with
				"echo: write error: File too large"

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/594f409e2c543e90fd836b78188dfa5c575065ba.1622867594.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Ritesh Harjani 2021-06-05 10:39:32 +05:30 committed by Theodore Ts'o
parent 6fed83957f
commit 75ca6ad408
1 changed files with 5 additions and 5 deletions
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10
fs/ext4/super.c
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@ -3030,17 +3030,17 @@ 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)
{
loff_t res = EXT4_NDIR_BLOCKS;
unsigned long long upper_limit, res = EXT4_NDIR_BLOCKS;
int meta_blocks;
loff_t upper_limit;
/* This is calculated to be the largest file size for a dense, block
/*
* This is calculated to be the largest file size for a dense, block
* mapped file such that the file's total number of 512-byte sectors,
* including data and all indirect blocks, does not exceed (2^48 - 1).
*
* __u32 i_blocks_lo and _u16 i_blocks_high represent the total
* number of 512-byte sectors of the file.
*/
if (!has_huge_files) {
/*
* !has_huge_files or implies that the inode i_block field
@ -3083,7 +3083,7 @@ static loff_t ext4_max_bitmap_size(int bits, int has_huge_files)
if (res > MAX_LFS_FILESIZE)
res = MAX_LFS_FILESIZE;
return res;
return (loff_t)res;
}
static ext4_fsblk_t descriptor_loc(struct super_block *sb,