In the Linux kernel, the following vulnerability has been resolved: btrfs: fix NULL dereference on root when tracing inode eviction When evicting an inode the first thing we do is to setup tracing for it, which implies fetching the root's id. But in btrfs_evict_inode() the root might be NULL, as implied in the next check that we do in btrfs_evict_inode(). Hence, we either should set the ->root_objectid to 0 in case the root is NULL, or we move tracing setup after checking that the root is not NULL. Setting the rootid to 0 at least gives us the possibility to trace this call even in the case when the root is NULL, so that's the solution taken here.
https://git.kernel.org/stable/c/f157dd661339fc6f5f2b574fe2429c43bd309534
https://git.kernel.org/stable/c/99e057f3d3ef24b99a7b1d84e01dd1bd890098da
https://git.kernel.org/stable/c/582ba48e4a4c06fef6bdcf4e57b7b9af660bbd0c