ext4: avoid overlapping preallocations due to overflow

stable inclusion
from stable-v5.10.200
commit 6b977a7323f7d932b5aa72952758056cf3a4b80f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8PI1H
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6b977a7323f7d932b5aa72952758056cf3a4b80f



--------------------------------

commit bedc5d34 upstream.

Let's say we want to allocate 2 blocks starting from 4294966386, after
predicting the file size, start is aligned to 4294965248, len is changed
to 2048, then end = start + size = 0x100000000. Since end is of
type ext4_lblk_t, i.e. uint, end is truncated to 0.

This causes (pa->pa_lstart >= end) to always hold when checking if the
current extent to be allocated crosses already preallocated blocks, so the
resulting ac_g_ex may cross already preallocated blocks. Hence we convert
the end type to loff_t and use pa_logical_end() to avoid overflow.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230724121059.11834-4-libaokun1@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Baokun Li <libaokun1@huawei.com>