But isn't it the return from do_dfs_failover the issue ... we checked
right before we called it on line 3561 ... but if it fails to populate
ses ... then we break out of the loop - we could change it to "goto
error" but the change in the patch is a little broader (wait until we
exit the while loop)
On Tue, Jul 13, 2021 at 11:54 PM Shyam Prasad N <nspmangalore@xxxxxxxxx> wrote:
>
> On Wed, Jul 14, 2021 at 6:19 AM Steve French <smfrench@xxxxxxxxx> wrote:
> >
> > Although it is unlikely to be have ended up with a null
> > session pointer calling cifs_try_adding_channels in cifs_mount.
> > Coverity correctly notes that we are already checking for
> > it earlier (when we return from do_dfs_failover), so at
> > a minimum to clarify the code we should make sure we also
> > check for it when we exit the loop so we don't end up calling
> > cifs_try_adding_channels or mount_setup_tlink with a null
> > ses pointer.
> >
> > Addresses-Coverity: 1505608 ("Derefernce after null check")
> > Reviewed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxx>
> > Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
> > ---
> > fs/cifs/connect.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> > index db6c607269f5..463cae116c12 100644
> > --- a/fs/cifs/connect.c
> > +++ b/fs/cifs/connect.c
> > @@ -3577,7 +3577,7 @@ int cifs_mount(struct cifs_sb_info *cifs_sb,
> > struct smb3_fs_context *ctx)
> > rc = -ELOOP;
> > } while (rc == -EREMOTE);
> >
> > - if (rc || !tcon)
> > + if (rc || !tcon || !ses)
> > goto error;
> >
> > kfree(ref_path);
> >
> > --
> > Thanks,
> >
> > Steve
>
> Hi Paulo,
>
> Doesn't it make sense to check rc, tcon and ses values right after
> mount_get_conns call?
>
> rc = mount_get_conns(ctx, cifs_sb, &xid, &server, &ses,
> &tcon); <<<<<<<<<<<<<<<<<<<
> /*
> * If called with 'nodfs' mount option, then skip DFS
> resolving. Otherwise unconditionally
> * try to get an DFS referral (even cached) to determine
> whether it is an DFS mount.
> *
> * Skip prefix path to provide support for DFS referrals from
> w2k8 servers which don't seem
> * to respond with PATH_NOT_COVERED to requests that include the prefix.
> */
> if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
> dfs_cache_find(xid, ses, cifs_sb->local_nls,
> cifs_remap(cifs_sb), ctx->UNC + 1, NULL,
> NULL)) {
> if (rc)
> goto error;
> /* Check if it is fully accessible and then mount it */
> rc = is_path_remote(cifs_sb, ctx, xid, server, tcon);
> if (!rc)
> goto out;
> if (rc != -EREMOTE)
> goto error;
> }
>
> Why don't we check for all rc values that we don't expect, and call
> dfs_cache_find only when it's an expected error?
>
> --
> Regards,
> Shyam
--
Thanks,
Steve
