CVE-2023-53187: In the Linux kernel, the following vulnerability has been resolved:  btrfs: fix use-after-free of new block group that became unused  If a task creates a new block group and that block group becomes unused before we finish its creation, at btrfs_create_pending_block_groups(), then when btrfs_mark_bg_unused() is called against the block group, we assume that the block group is currently in the list of block groups to reclaim, and we move it out of the list of new block groups and into the list of unused block groups. This has two consequences:  1) We move it out of the list of new block groups associated to the    current transaction. So the block group creation is not finished and    if we attempt to delete the bg because it's unused, we will not find    the block group item in the extent tree (or the new block group tree),    its device extent items in the device tree etc, resulting in the    deletion to fail due to the missing items;  2) We don't increment the reference count on the block group when we    move it to the list of unused block groups, because we assumed the    block group was on the list of block groups to reclaim, and in that    case it already has the correct reference count. However the block    group was on the list of new block groups, in which case no extra    reference was taken because it's local to the current task. This    later results in doing an extra reference count decrement when    removing the block group from the unused list, eventually leading the    reference count to 0.  This second case was caught when running generic/297 from fstests, which produced the following assertion failure and stack trace:    [589.559] assertion failed: refcount_read(&block_group->refs) == 1, in fs/btrfs/block-group.c:4299   [589.559] ------------[ cut here ]------------   [589.559] kernel BUG at fs/btrfs/block-group.c:4299!   [589.560] invalid opcode: 0000 [#1] PREEMPT SMP PTI   [589.560] CPU: 8 PID: 2819134 Comm: umount Tainted: G        W          6.4.0-rc6-btrfs-next-134+ #1   [589.560] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014   [589.560] RIP: 0010:btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.561] Code: 68 62 da c0 (...)   [589.561] RSP: 0018:ffffa55a8c3b3d98 EFLAGS: 00010246   [589.561] RAX: 0000000000000058 RBX: ffff8f030d7f2000 RCX: 0000000000000000   [589.562] RDX: 0000000000000000 RSI: ffffffff953f0878 RDI: 00000000ffffffff   [589.562] RBP: ffff8f030d7f2088 R08: 0000000000000000 R09: ffffa55a8c3b3c50   [589.562] R10: 0000000000000001 R11: 0000000000000001 R12: ffff8f05850b4c00   [589.562] R13: ffff8f030d7f2090 R14: ffff8f05850b4cd8 R15: dead000000000100   [589.563] FS:  00007f497fd2e840(0000) GS:ffff8f09dfc00000(0000) knlGS:0000000000000000   [589.563] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033   [589.563] CR2: 00007f497ff8ec10 CR3: 0000000271472006 CR4: 0000000000370ee0   [589.563] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000   [589.564] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400   [589.564] Call Trace:   [589.564]  <TASK>   [589.565]  ? __die_body+0x1b/0x60   [589.565]  ? die+0x39/0x60   [589.565]  ? do_trap+0xeb/0x110   [589.565]  ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.566]  ? do_error_trap+0x6a/0x90   [589.566]  ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.566]  ? exc_invalid_op+0x4e/0x70   [589.566]  ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.567]  ? asm_exc_invalid_op+0x16/0x20   [589.567]  ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.567]  ? btrfs_free_block_groups+0x449/0x4a0 [btrfs]   [589.567]  close_ctree+0x35d/0x560 [btrfs]   [589.568]  ? fsnotify_sb_delete+0x13e/0x1d0   [589.568]  ? dispose_list+0x3a/0x50   [589.568]  ? evict_inodes+0x151/0x1a0   [589.568]  generic_shutdown_super+0x73/0x1a0   [589.569]  kill_anon_super+0x14/0x30   [589.569]  btrfs_kill_super+0x12/0x20 [btrfs]   [589.569]  deactivate_locked ---truncated---