btrfs: do not BUG_ON() when freeing tree block after error

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: do not BUG_ON() when freeing tree block after error When freeing a tree block, at btrfs_free_tree_block(), if we fail to create a delayed reference we don't deal with the error and just do a BUG_ON(). The error most likely to happen is -ENOMEM, and we have a comment mentioning that only -ENOMEM can happen, but that is not true, because in case qgroups are enabled any error returned from btrfs_qgroup_trace_extent_post() (can be -EUCLEAN or anything returned from btrfs_search_slot() for example) can be propagated back to btrfs_free_tree_block(). So stop doing a BUG_ON() and return the error to the callers and make them abort the transaction to prevent leaking space. Syzbot was triggering this, likely due to memory allocation failure injection.

References

• https://git.kernel.org/stable/c/22d907bcd283d69d5e60497fc0d51969545c583b
• https://git.kernel.org/stable/c/98251cd60b4d702a8a81de442ab621e83a3fb24f
• https://git.kernel.org/stable/c/bb3868033a4cccff7be57e9145f2117cbdc91c11