[PATCH] btrfs: Fix potential null pointer deref

From: Alex Dewar
Date: Mon Sep 21 2020 - 15:13:26 EST

In btrfs_destroy_inode(), the variable root may be NULL, but the check
for this takes place after its value has already been dereferenced to
access its fs_info member. Move the dereference operation to later in
the function.

Fixes: a6dbd429d8dd ("Btrfs: fix panic when trying to destroy a newly allocated")
Addresses-Coverity: CID 1497103: Null pointer dereferences (REVERSE_INULL)
Signed-off-by: Alex Dewar <a.dewar@xxxxxxxxxxxx>
fs/btrfs/inode.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a5dae53c1e27..8f230b7bfe65 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8648,7 +8648,6 @@ void btrfs_destroy_inode(struct inode *vfs_inode)
struct btrfs_ordered_extent *ordered;
struct btrfs_inode *inode = BTRFS_I(vfs_inode);
struct btrfs_root *root = inode->root;
- struct btrfs_fs_info *fs_info = root->fs_info;

@@ -8673,7 +8672,7 @@ void btrfs_destroy_inode(struct inode *vfs_inode)
if (!ordered)
else {
- btrfs_err(fs_info,
+ btrfs_err(root->fs_info,
"found ordered extent %llu %llu on inode cleanup",
ordered->file_offset, ordered->num_bytes);
btrfs_remove_ordered_extent(inode, ordered);