CVE-2025-38222 ext4: inline: fix len overflow in ext4_prepare_inline_data
In the Linux kernel, the following vulnerability has been resolved:

ext4: inline: fix len overflow in ext4_prepare_inline_data

When running the following code on an ext4 filesystem with inline_data
feature enabled, it will lead to the bug below.

        fd = open("file1", O_RDWR | O_CREAT | O_TRUNC, 0666);
        ftruncate(fd, 30);
        pwrite(fd, "a", 1, (1UL << 40) + 5UL);

That happens because write_begin will succeed as when
ext4_generic_write_inline_data calls ext4_prepare_inline_data, pos + len
will be truncated, leading to ext4_prepare_inline_data parameter to be 6
instead of 0x10000000006.

Then, later when write_end is called, we hit:

        BUG_ON(pos + len > EXT4_I(inode)->i_inline_size);

at ext4_write_inline_data.

Fix it by using a loff_t type for the len parameter in
ext4_prepare_inline_data instead of an unsigned int.

[   44.545164] ------------[ cut here ]------------
[   44.545530] kernel BUG at fs/ext4/inline.c:240!
[   44.545834] Oops: invalid opcode: 0000 [#1] SMP NOPTI
[   44.546172] CPU: 3 UID: 0 PID: 343 Comm: test Not tainted 6.15.0-rc2-00003-g9080916f4863 #45 PREEMPT(full)  112853fcebfdb93254270a7959841d2c6aa2c8bb
[   44.546523] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   44.546523] RIP: 0010:ext4_write_inline_data+0xfe/0x100
[   44.546523] Code: 3c 0e 48 83 c7 48 48 89 de 5b 41 5c 41 5d 41 5e 41 5f 5d e9 e4 fa 43 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 0f 0b <0f> 0b 0f 1f 44 00 00 55 41 57 41 56 41 55 41 54 53 48 83 ec 20 49
[   44.546523] RSP: 0018:ffffb342008b79a8 EFLAGS: 00010216
[   44.546523] RAX: 0000000000000001 RBX: ffff9329c579c000 RCX: 0000010000000006
[   44.546523] RDX: 000000000000003c RSI: ffffb342008b79f0 RDI: ffff9329c158e738
[   44.546523] RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
[   44.546523] R10: 00007ffffffff000 R11: ffffffff9bd0d910 R12: 0000006210000000
[   44.546523] R13: fffffc7e4015e700 R14: 0000010000000005 R15: ffff9329c158e738
[   44.546523] FS:  00007f4299934740(0000) GS:ffff932a60179000(0000) knlGS:0000000000000000
[   44.546523] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   44.546523] CR2: 00007f4299a1ec90 CR3: 0000000002886002 CR4: 0000000000770eb0
[   44.546523] PKRU: 55555554
[   44.546523] Call Trace:
[   44.546523]  <TASK>
[   44.546523]  ext4_write_inline_data_end+0x126/0x2d0
[   44.546523]  generic_perform_write+0x17e/0x270
[   44.546523]  ext4_buffered_write_iter+0xc8/0x170
[   44.546523]  vfs_write+0x2be/0x3e0
[   44.546523]  __x64_sys_pwrite64+0x6d/0xc0
[   44.546523]  do_syscall_64+0x6a/0xf0
[   44.546523]  ? __wake_up+0x89/0xb0
[   44.546523]  ? xas_find+0x72/0x1c0
[   44.546523]  ? next_uptodate_folio+0x317/0x330
[   44.546523]  ? set_pte_range+0x1a6/0x270
[   44.546523]  ? filemap_map_pages+0x6ee/0x840
[   44.546523]  ? ext4_setattr+0x2fa/0x750
[   44.546523]  ? do_pte_missing+0x128/0xf70
[   44.546523]  ? security_inode_post_setattr+0x3e/0xd0
[   44.546523]  ? ___pte_offset_map+0x19/0x100
[   44.546523]  ? handle_mm_fault+0x721/0xa10
[   44.546523]  ? do_user_addr_fault+0x197/0x730
[   44.546523]  ? do_syscall_64+0x76/0xf0
[   44.546523]  ? arch_exit_to_user_mode_prepare+0x1e/0x60
[   44.546523]  ? irqentry_exit_to_user_mode+0x79/0x90
[   44.546523]  entry_SYSCALL_64_after_hwframe+0x55/0x5d
[   44.546523] RIP: 0033:0x7f42999c6687
[   44.546523] Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
[   44.546523] RSP: 002b:00007ffeae4a7930 EFLAGS: 00000202 ORIG_RAX: 0000000000000012
[   44.546523] RAX: ffffffffffffffda RBX: 00007f4299934740 RCX: 00007f42999c6687
[   44.546523] RDX: 0000000000000001 RSI: 000055ea6149200f RDI: 0000000000000003
[   44.546523] RBP: 00007ffeae4a79a0 R08: 0000000000000000 R09: 0000000000000000
[   44.546523] R10: 0000010000000005 R11: 0000000000000202 R12: 0000
---truncated---
CVSS v3.1 score: 5.5