btrfs: release correct delalloc amount in direct IO write path

In the Linux kernel, the following vulnerability has been resolved:

btrfs: release correct delalloc amount in direct IO write path

Running generic/406 causes the following WARNING in btrfs_destroy_inode()

which tells there are outstanding extents left.

In btrfs_get_blocks_direct_write(), we reserve a temporary outstanding

extents with btrfs_delalloc_reserve_metadata() (or indirectly from

btrfs_delalloc_reserve_space(()). We then release the outstanding extents

with btrfs_delalloc_release_extents(). However, the "len" can be modified

in the COW case, which releases fewer outstanding extents than expected.

Fix it by calling btrfs_delalloc_release_extents() for the original length.

To reproduce the warning, the filesystem should be 1 GiB. It's

triggering a short-write, due to not being able to allocate a large

extent and instead allocating a smaller one.

WARNING: CPU: 0 PID: 757 at fs/btrfs/inode.c:8848 btrfs_destroy_inode+0x1e6/0x210 [btrfs]

Modules linked in: btrfs blake2b_generic xor lzo_compress

lzo_decompress raid6_pq zstd zstd_decompress zstd_compress xxhash zram

zsmalloc

CPU: 0 PID: 757 Comm: umount Not tainted 5.17.0-rc8+ #101

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS d55cb5a 04/01/2014

RIP: 0010:btrfs_destroy_inode+0x1e6/0x210 [btrfs]

RSP: 0018:ffffc9000327bda8 EFLAGS: 00010206

RAX: 0000000000000000 RBX: ffff888100548b78 RCX: 0000000000000000

RDX: 0000000000026900 RSI: 0000000000000000 RDI: ffff888100548b78

RBP: ffff888100548940 R08: 0000000000000000 R09: ffff88810b48aba8

R10: 0000000000000001 R11: ffff8881004eb240 R12: ffff88810b48a800

R13: ffff88810b48ec08 R14: ffff88810b48ed00 R15: ffff888100490c68

FS: 00007f8549ea0b80(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f854a09e733 CR3: 000000010a2e9003 CR4: 0000000000370eb0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

destroy_inode+0x33/0x70

dispose_list+0x43/0x60

evict_inodes+0x161/0x1b0

generic_shutdown_super+0x2d/0x110

kill_anon_super+0xf/0x20

btrfs_kill_super+0xd/0x20 [btrfs]

deactivate_locked_super+0x27/0x90

cleanup_mnt+0x12c/0x180

task_work_run+0x54/0x80

exit_to_user_mode_prepare+0x152/0x160

syscall_exit_to_user_mode+0x12/0x30

do_syscall_64+0x42/0x80

entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7f854a000fb7