btrfs: Handle uninitialised inode eviction

The code flow in btrfs_new_inode allows for btrfs_evict_inode to be
called with not fully initialised inode (e.g. ->root member not
being set). This can happen when btrfs_set_inode_index in
btrfs_new_inode fails, which in turn would call iput for the newly
allocated inode. This in turn leads to vfs calling into btrfs_evict_inode.
This leads to null pointer dereference. To handle this situation check whether
the passed inode has root set and just free it in case it doesn't.

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3e61bd1f3f65..5c2c076bc552 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5159,11 +5159,18 @@ void btrfs_evict_inode(struct inode *inode)
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_block_rsv *rsv, *global_rsv;
         int steal_from_global = 0;
-        u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
+        u64 min_size;
         int ret;
 
         trace_btrfs_inode_evict(inode);
 
+        if (!root) {
+                kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
+                return;
+        }
+
+        min_size = btrfs_calc_trunc_metadata_size(root, 1);
+
         evict_inode_truncate_pages(inode);
 
         if (inode->i_nlink &&