linux-kernel - [PATCH] hugetlbfs: make BUG_ON(!inode) takes effect in hugetlbfs

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Date:   Sat, 16 Jan 2021 04:09:10 -0500
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <mike.kravetz@...cle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] hugetlbfs: make BUG_ON(!inode) takes effect in hugetlbfs_setattr

When we reach here with inode = NULL, we should have crashed as inode has
already been dereferenced via hstate_inode. In order to make BUG_ON(!inode)
takes effect, we should defer initializing hstate until we really need it.
Also do this for hugetlbfs_inode_info as it's only used when ia_valid is
verified with ATTR_SIZE.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 fs/hugetlbfs/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 740693d7f255..9b221b87fbea 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -755,10 +755,8 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
 static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
 {
 	struct inode *inode = d_inode(dentry);
-	struct hstate *h = hstate_inode(inode);
 	int error;
 	unsigned int ia_valid = attr->ia_valid;
-	struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
 
 	BUG_ON(!inode);
 
@@ -767,6 +765,8 @@ static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
 		return error;
 
 	if (ia_valid & ATTR_SIZE) {
+		struct hstate *h = hstate_inode(inode);
+		struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
 		loff_t oldsize = inode->i_size;
 		loff_t newsize = attr->ia_size;
 
-- 
2.19.1