On Fri, 2010-04-23 at 13:43 +0200, Dan Carpenter wrote:
> > > This is a Smatch bug that has me a little puzzled.
> > >
> > > drivers/net/wireless/iwmc3200wifi/debugfs.c +447 iwm_debugfs_init(26)
> > > warn: 'iwm->dbg.devdir' dereferencing possible ERR_PTR()
> > >
> > > 440 iwm->dbg.devdir = debugfs_create_dir(devdir, iwm->dbg.rootdir);
> > > 441 result = PTR_ERR(iwm->dbg.devdir);
> > > 442 if (IS_ERR(iwm->dbg.devdir) && (result != -ENODEV)) {
> > > 443 IWM_ERR(iwm, "Couldn't create devdir: %d\n", result);
> > > 444 goto error;
> > > 445 }
> > > 446
> > > 447 iwm->dbg.dbgdir = debugfs_create_dir("debug", iwm->dbg.devdir);
> > >
> > > It looks like "iwm->dbg.devdir" could be ERR_PTR(-ENODEV) on line 447 and
> > > that would cause a problem inside debugfs_create_dir(). But at the same
> > > time -ENODEV was deliberately singled out as OK from other possible errors
> > > that debugfs_create_dir() can return.
> >
> > We take -ENODEV for debugfs_create_dir if CONFIG_DEBUG_FS is not
> > enabled. We returns 0 deliberately in this case for rootdir create. I
> > agree we don't need to check it for the subdirs like we did now. But I
> > found lots of code don't even check (or don't use IS_ERR to check) the
> > return value of debugfs_create_dir. Maybe that's more problematic?
>
> Ah. Thanks for the explanation.
>
> The bit that was problematic in this code for me is that passing
> ERR_PTR(-ENODEV) to debugfs_create_dir() on line 447 will cause an oops.
> But, as you point out, the check on line 442 is never true because we
> already established that debugfs is enabled.
I don't think so. See, that function will only return -ENODEV when
debugfs is not compiled into the kernel, and in that case the argument
to debugfs_create_dir is never used anyway.
johannes
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