On Tue, 2022-07-26 at 16:23 -0400, Jeff Layton wrote: > NFS server is exporting a sticky directory (mode 01777) with root > squashing enabled. Client has protect_regular enabled and then tries to > open a file as root in that directory. File is created (with ownership > set to nobody:nobody) but the open syscall returns an error. > > The problem is may_create_in_sticky, which rejects the open even though > the file has already been created/opened. Only call may_create_in_sticky > if the file hasn't already been opened or created. > > Cc: Christian Brauner <brauner@xxxxxxxxxx> > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1976829 > Reported-by: Yongchen Yang <yoyang@xxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > fs/namei.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/fs/namei.c b/fs/namei.c > index 1f28d3f463c3..7480b6dc8d27 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -3495,10 +3495,15 @@ static int do_open(struct nameidata *nd, > return -EEXIST; > if (d_is_dir(nd->path.dentry)) > return -EISDIR; > - error = may_create_in_sticky(mnt_userns, nd, > - d_backing_inode(nd->path.dentry)); > - if (unlikely(error)) > - return error; > + if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) { > + error = may_create_in_sticky(mnt_userns, nd, > + d_backing_inode(nd->path.dentry)); > + if (unlikely(error)) { > + printk("%s: f_mode=0x%x oflag=0x%x\n", > + __func__, file->f_mode, open_flag); > + return error; > + } > + } > } > if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) > return -ENOTDIR; I'm pretty sure this patch is the wrong approach, actually, since it doesn't fix the regular (non-atomic) open codepath. Any thoughts on what the right fix might be? -- Jeff Layton <jlayton@xxxxxxxxxx>
