btrfs: exit after state insertion failure at btrfs_convert_extent_bit()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: exit after state insertion failure at btrfs_convert_extent_bit() If insert_state() state failed it returns an error pointer and we call extent_io_tree_panic() which will trigger a BUG() call. However if CONFIG_BUG is disabled, which is an uncommon and exotic scenario, then we fallthrough and call cache_state() which will dereference the error pointer, resulting in an invalid memory access. So jump to the 'out' label after calling extent_io_tree_panic(), it also makes the code more clear besides dealing with the exotic scenario where CONFIG_BUG is disabled.

References

• https://git.kernel.org/stable/c/58c50f45e1821a04d61b62514f9bd34afe67c622
• https://git.kernel.org/stable/c/8d9d32088e304e2bc444a3087cab0bbbd9951866
• https://git.kernel.org/stable/c/3bf179e36da917c5d9bec71c714573ed1649b7c1