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;