On Fri, May 15, 2020 at 09:13:57PM +0100, Al Viro wrote:
> On Sat, May 16, 2020 at 12:36:28AM +0900, Tetsuo Handa wrote:
> > On 2020/05/16 0:18, Tetsuo Handa wrote:
[snip]
> > A similar bug (racing inode destruction with open() on proc filesystem) was fixed as
> > commit 6f7c41374b62fd80 ("tomoyo: Don't use nifty names on sockets."). Then, it might
> > not be safe to replace dentry->d_sb->s_fs_info with dentry->d_inode->i_sb->s_fs_info .
>
> Could you explain why do you want to bother with d_inode() anyway? Anything that
> does dentry->d_inode->i_sb can bloody well use dentry->d_sb. And that's never
> changed over the struct dentry lifetime - ->d_sb is set on allocation and never
> modified afterwards.
Incidentally, this
r_ino = nfs_fhget(ss_mnt->mnt_root->d_inode->i_sb, src_fh, &fattr,
NULL);
(in nfs42_ssc_open()) is just plain weird.
1) d->d_inode->i_sb is equal to d->d_sb
2) m->mnt_root->d_sb is equal to m->mnt_sb
IOW, the whole thing should be
r_ino = nfs_fhget(ss_mnt->mnt_sb, src_fh, &fattr, NULL);
Moreover,
server = NFS_SERVER(ss_mnt->mnt_root->d_inode);
in the same function is again too convoluted for no good reason, seeing that
NFS_SERVER(inode) is NFS_SB(inode->i_sb).
Something along the lines of
nfs: don't obfuscate ->mnt_sb as ->mnt_root->d_inode->i_sb
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 8e5d6223ddd3..1e8ca45bc806 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -317,15 +317,14 @@ nfs42_ssc_open(struct vfsmount *ss_mnt, struct nfs_fh *src_fh,
{
struct nfs_fattr fattr;
struct file *filep, *res;
- struct nfs_server *server;
+ struct super_block *sb = ss_mnt->mnt_sb;
+ struct nfs_server *server = NFS_SB(sb);
struct inode *r_ino = NULL;
struct nfs_open_context *ctx;
struct nfs4_state_owner *sp;
char *read_name = NULL;
int len, status = 0;
- server = NFS_SERVER(ss_mnt->mnt_root->d_inode);
-
nfs_fattr_init(&fattr);
status = nfs4_proc_getattr(server, src_fh, &fattr, NULL, NULL);
@@ -341,8 +340,7 @@ nfs42_ssc_open(struct vfsmount *ss_mnt, struct nfs_fh *src_fh,
goto out;
snprintf(read_name, len, SSC_READ_NAME_BODY, read_name_gen++);
- r_ino = nfs_fhget(ss_mnt->mnt_root->d_inode->i_sb, src_fh, &fattr,
- NULL);
+ r_ino = nfs_fhget(sb, src_fh, &fattr, NULL);
if (IS_ERR(r_ino)) {
res = ERR_CAST(r_ino);
goto out_free_name;
