The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 75ca6ad408f459f00b09a64f04c774559848c097 Mon Sep 17 00:00:00 2001

From: Ritesh Harjani riteshh@linux.ibm.com Date: Sat, 5 Jun 2021 10:39:32 +0530 Subject: [PATCH] ext4: fix loff_t overflow in ext4_max_bitmap_size()

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.162286759... Signed-off-by: Theodore Ts'o tytso@mit.edu

diff --git a/fs/ext4/super.c b/fs/ext4/super.c index a52f1572daa5..9b5b2f63b470 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -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,