Re: [PATCH 3/3] virtiofsd: Check file type in lo_flush()

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Dec 10, 2020 at 08:14:31PM +0000, Dr. David Alan Gilbert wrote:
> * Vivek Goyal (vgoyal@redhat.com) wrote:
> > On Thu, Dec 10, 2020 at 08:03:03PM +0000, Dr. David Alan Gilbert wrote:
> > > * Vivek Goyal (vgoyal@redhat.com) wrote:
> > > > Currently lo_flush() is written in such a way that it expects to receive
> > > > a FLUSH requests on a regular file (and not directories). For example,
> > > > we call lo_fi_fd() which searches lo->fd_map. If we open directories
> > > > using opendir(), we keep don't keep track of these in lo->fd_map instead
> > > > we keep them in lo->dir_map. So we expect lo_flush() to be called on
> > > > regular files only.
> > > > 
> > > > Even linux fuse client calls FLUSH only for regular files and not
> > > > directories. So put a check for filetype and return EBADF if
> > > > lo_flush() is called on a non-regular file.
> > > > 
> > > > Reported-by: Laszlo Ersek <lersek@redhat.com>
> > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > > > ---
> > > >  tools/virtiofsd/passthrough_ll.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > > > index 8ba79f503a..48a109d3f6 100644
> > > > --- a/tools/virtiofsd/passthrough_ll.c
> > > > +++ b/tools/virtiofsd/passthrough_ll.c
> > > > @@ -1968,7 +1968,7 @@ static void lo_flush(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi)
> > > >      struct lo_data *lo = lo_data(req);
> > > >  
> > > >      inode = lo_inode(req, ino);
> > > > -    if (!inode) {
> > > > +    if (!inode || !S_ISREG(inode->filetype)) {
> > > >          fuse_reply_err(req, EBADF);
> > > 
> > > Does that need a lo_inode_put(lo, &inode) in the new case?
> > 
> > Good catch. Yes if inode is valid but file type is not regular, we need
> > to put inode reference.
> > 
> > Do you want me to post a new patch or you will like to take care of
> > it.
> 
> OK, so if we make this :
> 
>   if (!inode) {
>       fuse_reply_err(req, EBADF);
>       return;
>   }
> 
>   if (!S_ISREG(inode->filetype)) {
>       lo_inode_put(lo_data(req), &inode);
>       fuse_reply_err(req, EBADF);
>       return;
>   }
> 
> (Untested)

Hi Dave,

Above looks good. For your convenience, I updated the patch and also
tested it by running blogbench and things look fine.

Vivek

Subject: virtiofsd: Check file type in lo_flush()

Currently lo_flush() is written in such a way that it expects to receive
a FLUSH requests on a regular file (and not directories). For example,
we call lo_fi_fd() which searches lo->fd_map. If we open directories
using opendir(), we keep don't keep track of these in lo->fd_map instead
we keep them in lo->dir_map. So we expect lo_flush() to be called on
regular files only.

Even linux fuse client calls FLUSH only for regular files and not
directories. So put a check for filetype and return EBADF if 
lo_flush() is called on a non-regular file.

Reported-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 tools/virtiofsd/passthrough_ll.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: rhvgoyal-qemu/tools/virtiofsd/passthrough_ll.c
===================================================================
--- rhvgoyal-qemu.orig/tools/virtiofsd/passthrough_ll.c	2020-12-11 09:00:28.787669761 -0500
+++ rhvgoyal-qemu/tools/virtiofsd/passthrough_ll.c	2020-12-11 09:03:38.239496505 -0500
@@ -1973,6 +1973,12 @@ static void lo_flush(fuse_req_t req, fus
         return;
     }
 
+    if (!S_ISREG(inode->filetype)) {
+        lo_inode_put(lo, &inode);
+        fuse_reply_err(req, EBADF);
+        return;
+    }
+
     /* An fd is going away. Cleanup associated posix locks */
     if (lo->posix_lock) {
         pthread_mutex_lock(&inode->plock_mutex);