btrfs: fix qgroup reserve leaks in cow_file_range

CVE-2024-46733

What is CVE-2024-46733?

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

btrfs: fix qgroup reserve leaks in cow_file_range

In the buffered write path, the dirty page owns the qgroup reserve until it creates an ordered_extent.

Therefore, any errors that occur before the ordered_extent is created must free that reservation, or else the space is leaked. The fstest generic/475 exercises various IO error paths, and is able to trigger errors in cow_file_range where we fail to get to allocating the ordered extent. Note that because we do clear delalloc, we are likely to remove the inode from the delalloc list, so the inodes/pages to not have invalidate/launder called on them in the commit abort path.

This results in failures at the unmount stage of the test that look like:

BTRFS: error (device dm-8 state EA) in cleanup_transaction:2018: errno=-5 IO failure BTRFS: error (device dm-8 state EA) in btrfs_replace_file_extents:2416: errno=-5 IO failure BTRFS warning (device dm-8 state EA): qgroup 0/5 has unreleased space, type 0 rsv 28672 ------------[ cut here ]------------ WARNING: CPU: 3 PID: 22588 at fs/btrfs/disk-io.c:4333 close_ctree+0x222/0x4d0 [btrfs] Modules linked in: btrfs blake2b_generic libcrc32c xor zstd_compress raid6_pq CPU: 3 PID: 22588 Comm: umount Kdump: loaded Tainted: G W 6.10.0-rc7-gab56fde445b8 #21 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 RIP: 0010:close_ctree+0x222/0x4d0 [btrfs] RSP: 0018:ffffb4465283be00 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffffa1a1818e1000 RCX: 0000000000000001 RDX: 0000000000000000 RSI: ffffb4465283bbe0 RDI: ffffa1a19374fcb8 RBP: ffffa1a1818e13c0 R08: 0000000100028b16 R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000003 R12: ffffa1a18ad7972c R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f9168312b80(0000) GS:ffffa1a4afcc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f91683c9140 CR3: 000000010acaa000 CR4: 00000000000006f0 Call Trace: ? close_ctree+0x222/0x4d0 [btrfs] ? __warn.cold+0x8e/0xea ? close_ctree+0x222/0x4d0 [btrfs] ? report_bug+0xff/0x140 ? handle_bug+0x3b/0x70 ? exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ? close_ctree+0x222/0x4d0 [btrfs] generic_shutdown_super+0x70/0x160 kill_anon_super+0x11/0x40 btrfs_kill_super+0x11/0x20 [btrfs] deactivate_locked_super+0x2e/0xa0 cleanup_mnt+0xb5/0x150 task_work_run+0x57/0x80 syscall_exit_to_user_mode+0x121/0x130 do_syscall_64+0xab/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f916847a887 ---[ end trace 0000000000000000 ]--- BTRFS error (device dm-8 state EA): qgroup reserved space leaked

Cases 2 and 3 in the out_reserve path both pertain to this type of leak and must free the reserved qgroup data. Because it is already an error path, I opted not to handle the possible errors in btrfs_free_qgroup_data.

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References