Re: [PATCH] hugetlbfs: make BUG_ON(!inode) takes effect in hugetlbfs_setattr

[Miaohe Lin]

Hi:

On 2021/1/18 15:59, Muchun Song wrote:
> On Sat, Jan 16, 2021 at 5:11 PM Miaohe Lin  wrote:
>>
>> 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 
>> ---
>>  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);
> 
> If inode == NULL, it will panic here when we access inode->i_sb.
> I have seen many other file system implementations about setattr,
> they all think that d_inode() will return a non-NULL pointer. So
> I prefer to just remove the BUG_ON().
> 

Sounds reasonable. Will do it in v2. Many thanks.

> Thanks.
> 
> 
>> 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
>>
> .
> 

Re: [PATCH] hugetlbfs: make BUG_ON(!inode) takes effect in hugetlbfs_setattr

[Muchun Song]

On Sat, Jan 16, 2021 at 5:11 PM Miaohe Lin  wrote:
>
> 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 
> ---
>  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);

If inode == NULL, it will panic here when we access inode->i_sb.
I have seen many other file system implementations about setattr,
they all think that d_inode() will return a non-NULL pointer. So
I prefer to just remove the BUG_ON().

Thanks.


> 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
>

[PATCH] hugetlbfs: make BUG_ON(!inode) takes effect in hugetlbfs_setattr

[Miaohe Lin]

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 
---
 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