linux-kernel - Re: [PATCH] fs: fs_parser: avoid NULL param->string to kstrtouint

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Date:   Sat, 20 Jul 2019 07:29:20 +0800
From:   YinFengwei <nh26223.lmm@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Yin Fengwei <nh26223.lmm@...il.com>, dhowells@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, miklos@...redi.hu,
        viro@...iv.linux.org.uk, tglx@...utronix.de,
        kstewart@...uxfoundation.org
Subject: Re: [PATCH] fs: fs_parser: avoid NULL param->string to kstrtouint

On Fri, Jul 19, 2019 at 07:38:11PM +0200, Greg KH wrote:
> On Fri, Jul 19, 2019 at 08:43:29PM +0800, Yin Fengwei wrote:
> > syzbot reported general protection fault in kstrtouint:
> > https://lkml.org/lkml/2019/7/18/328
> > 
> > >From the log, if the mount option is something like:
> >    fd,XXXXXXXXXXXXXXXXXXXX
> > 
> > The default parameter (which has NULL param->string) will be
> > passed to vfs_parse_fs_param. Finally, this NULL param->string
> > is passed to kstrtouint and trigger NULL pointer access.
> > 
> > Reported-by: syzbot+398343b7c1b1b989228d@...kaller.appspotmail.com
> > Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
> > 
> > Signed-off-by: Yin Fengwei <nh26223.lmm@...il.com>
> > ---
> >  fs/fs_parser.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/fs/fs_parser.c b/fs/fs_parser.c
> > index d13fe7d797c2..578e6880ac67 100644
> > --- a/fs/fs_parser.c
> > +++ b/fs/fs_parser.c
> > @@ -210,6 +210,10 @@ int fs_parse(struct fs_context *fc,
> >  	case fs_param_is_fd: {
> >  		switch (param->type) {
> >  		case fs_value_is_string:
> > +			if (result->has_value) {
> > +				goto bad_value;
> > +			}
> 
> Always run checkpatch.pl so grumpy maintainers do not tell you to go run
> checkpatch.pl :)

Thanks a lot for kindly reminder. Will be careful for future patch. :)

Regards
Yin, Fengwei