CVE-2022-50293

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

btrfs: do not BUG_ON() on ENOMEM when dropping extent items for a range

If we get -ENOMEM while dropping file extent items in a given range, at btrfsdropextents(), due to failure to allocate memory when attempting to increment the reference count for an extent or drop the reference count, we handle it with a BUGON(). This is excessive, instead we can simply abort the transaction and return the error to the caller. In fact most callers of btrfsdropextents(), directly or indirectly, already abort the transaction if btrfsdrop_extents() returns any error.

Also, we already have error paths at btrfsdropextents() that may return -ENOMEM and in those cases we abort the transaction, like for example anything that changes the b+tree may return -ENOMEM due to a failure to allocate a new extent buffer when COWing an existing extent buffer, such as a call to btrfsduplicateitem() for example.

So replace the BUG_ON() calls with proper logic to abort the transaction and return the error.