Re: [PATCH] fs/ntfs3: fix null pointer dereference in d_flags_for_inode

[练亮斌 <jjm2473@gmail.com>]

Hello.

If ntfs_file_inode_operations is ok for $Extend, that's fine with me.

Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
于2022年6月1日周三 00:34写道：
>
> Hello.
>
> In the end of ntfs_read_mft function we must assign correct i_op:
> inode->i_op = &ntfs_dir_inode_operations;
> <...>
> inode->i_op = &ntfs_link_inode_operations;
> <...>
> inode->i_op = &ntfs_file_inode_operations;
> <...>
> inode->i_op = &ntfs_special_inode_operations;
>
> In this if .. else if .. else is an error:
> records in $Extend doesn't get correct i_op.
> This was fixed in my patch.
>
> Line in beginning of ntfs_read_mft function
> inode->i_op = NULL;
> triggered null pointer dereference because
> inode->i_op = &ntfs_file_inode_operations;
> is missing for records in $Extend.
>
> If I just remove inode->i_op = NULL,
> then in i_op will be some previous value.
> Sometimes this value is correct, sometimes it's not.
>
> I'm thankful, that you've spent time to find and debug this issue.
> This was reflected in line Reported-by: Liangbin Lian <jjm2473@gmail.com>
> I hope I've made more clear my previous message.
>
>
> On 5/28/22 16:42, 练亮斌 wrote:
> > Hello.
> > `inode->i_op` already initialized when inode alloc, this bug was
> > introduced by `inode->i_op = NULL;`, just delete this line.
> > Please check my patch, maybe it's a better one, I have tested it on my project.
> >
> > On 5/26/22 18:23, Almaz Alexandrovich wrote:
> >>
> >> Hello.
> >>
> >> Thank you for reporting this bug.
> >> The bug happens because we don't initialize i_op for records in $Extend.
> >> We tested patch on our side, let me know if patch helps you too.
> >>
> >>       fs/ntfs3: Fix missing i_op in ntfs_read_mft
> >>
> >>       There is null pointer dereference because i_op == NULL.
> >>       The bug happens because we don't initialize i_op for records in $Extend.
> >>       Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
> >>
> >>       Reported-by: Liangbin Lian <jjm2473@gmail.com>
> >>       Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
> >>
> >> diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
> >> index 879952254071..b2cc1191be69 100644
> >> --- a/fs/ntfs3/inode.c
> >> +++ b/fs/ntfs3/inode.c
> >> @@ -430,6 +430,7 @@ static struct inode *ntfs_read_mft(struct inode *inode,
> >>           } else if (fname && fname->home.low == cpu_to_le32(MFT_REC_EXTEND) &&
> >>                      fname->home.seq == cpu_to_le16(MFT_REC_EXTEND)) {
> >>                   /* Records in $Extend are not a files or general directories. */
> >> +               inode->i_op = &ntfs_file_inode_operations;
> >>           } else {
> >>                   err = -EINVAL;
> >>                   goto out;
> >>
> >>
> >> On 5/6/22 06:46, Liangbin Lian wrote:
> >>> ntfs_read_mft may return inode with null i_op, cause null pointer dereference in d_flags_for_inode (inode->i_op->get_link).
> >>> Reproduce:
> >>>    - sudo mount -t ntfs3 -o loop ntfs.img ntfs
> >>>    - ls ntfs/'$Extend/$Quota'
> >>>
> >>> The call trace is shown below (striped):
> >>>    BUG: kernel NULL pointer dereference, address: 0000000000000008
> >>>    CPU: 0 PID: 577 Comm: ls Tainted: G           OE     5.16.0-0.bpo.4-amd64 #1  Debian 5.16.12-1~bpo11+1
> >>>    RIP: 0010:d_flags_for_inode+0x65/0x90
> >>>    Call Trace:
> >>>    ntfs_lookup
> >>>    +--- dir_search_u
> >>>    |    +--- ntfs_iget5
> >>>    |         +--- ntfs_read_mft
> >>>    +--- d_splice_alias
> >>>         +--- __d_add
> >>>              +--- d_flags_for_inode
> >>>
> >>> Signed-off-by: Liangbin Lian <jjm2473@gmail.com>
> >>> ---
> >>>    fs/ntfs3/inode.c | 1 -
> >>>    1 file changed, 1 deletion(-)
> >>>
> >>> diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
> >>> index 9eab11e3b..b68d26fa8 100644
> >>> --- a/fs/ntfs3/inode.c
> >>> +++ b/fs/ntfs3/inode.c
> >>> @@ -45,7 +45,6 @@ static struct inode *ntfs_read_mft(struct inode *inode,
> >>>        struct MFT_REC *rec;
> >>>        struct runs_tree *run;
> >>>
> >>> -     inode->i_op = NULL;
> >>>        /* Setup 'uid' and 'gid' */
> >>>        inode->i_uid = sbi->options->fs_uid;
> >>>        inode->i_gid = sbi->options->fs_gid;