Re: [PATCH] mm: hugetlb: checking for IS_ERR() instead of NULL

From: Nigel Christian <nigel.l.christian@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mm: hugetlb: checking for IS_ERR() instead of NULL
Date: Fri, 4 Jun 2021 10:14:42 -0400	[thread overview]
Message-ID: <YLo1Ut1A6fIp5r1t@fedora> (raw)
In-Reply-To: <20210604133400.GL1955@kadam>

On Fri, Jun 04, 2021 at 04:34:00PM +0300, Dan Carpenter wrote:
> On Wed, Jun 02, 2021 at 05:47:52PM +0300, Dan Carpenter wrote:
> > On Tue, Jun 01, 2021 at 11:50:06PM +0300, Dan Carpenter wrote:
> > > On Tue, Jun 01, 2021 at 10:51:23PM +0300, Dan Carpenter wrote:
> > > > The other thing which might be interesting is if you pass a NULL
> > > > to IS_ERR() and then dereference the NULL then print a warning about
> > > > that.  This has a lot of overlaps with some of my existing checks, but
> > > > it's still a new idea so it belongs in a separate check.  It's fine and
> > > > good even if one bug triggers a lot of different warnings.  I'll write
> > > > that, hang on, brb.
> > > 
> > > 100% untested.  :)  I'll test it tonight.
> > > 
> > 
> 
> I also added a check for:
> 
> 	if (is_impossible_path())
> 		return;
> 
> to silence some of the false positives.  But the results are all still
> false positives.  They're "high quality" false positives, because often
> the code looks buggy.  I think that someone went through and fixed all
> the real bugs with this.

Double positives are good. Glad the bugs are getting fixed!
Back to hunting for deadcode. That seems to be the lowest
hanging fruit for me at the momemnt. (-_-)

> 
> I reported the snd_media_device_create() bug and sent a fix for the
> nfs_init_server() but the rest, I'm just going to leave.
> 
> sound/usb/media.c:287 snd_media_device_create() error: potential NULL/IS_ERR bug 'mdev'
> mm/mempolicy.c:1293 do_mbind() error: potential NULL/IS_ERR bug 'new'
> fs/nfs/client.c:701 nfs_init_server() error: potential NULL/IS_ERR bug 'clp'
> fs/afs/server.c:652 afs_update_server_record() error: potential NULL/IS_ERR bug 'alist'
> fs/afs/volume.c:322 afs_update_volume_status() error: potential NULL/IS_ERR bug 'vldb'
> fs/ubifs/lpt_commit.c:583 next_pnode_to_dirty() error: potential NULL/IS_ERR bug 'nnode'
> fs/ubifs/lpt_commit.c:583 next_pnode_to_dirty() error: potential NULL/IS_ERR bug 'nnode'
> fs/ntfs/attrib.c:2188 ntfs_attr_extend_allocation() error: potential NULL/IS_ERR bug 'rl'
> fs/ext4/namei.c:2375 ext4_add_entry() error: potential NULL/IS_ERR bug 'bh'
> drivers/pinctrl/renesas/core.c:1144 sh_pfc_probe() error: potential NULL/IS_ERR bug 'info'
> drivers/mfd/ene-kb3930.c:165 kb3930_probe() error: potential NULL/IS_ERR bug 'ddata->off_gpios'
> drivers/mtd/ubi/attach.c:409 add_volume() error: potential NULL/IS_ERR bug 'av'
> drivers/mtd/ubi/fastmap.c:185 add_vol() error: potential NULL/IS_ERR bug 'av'
> drivers/gpu/drm/nouveau/nvkm/engine/nvdec/base.c:57 nvkm_nvdec_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/engine/sec2/base.c:104 nvkm_sec2_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/engine/gr/gf100.c:2108 gf100_gr_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/engine/nvenc/base.c:59 nvkm_nvenc_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c:181 nvkm_pmu_ctor() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/base.c:56 nvkm_gsp_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/gpu/drm/nouveau/nvkm/subdev/acr/base.c:430 nvkm_acr_new_() error: potential NULL/IS_ERR bug 'fwif'
> drivers/clk/clk.c:417 clk_core_get() error: potential NULL/IS_ERR bug 'hw'
> drivers/platform/chrome/cros_ec_chardev.c:225 cros_ec_chardev_read() error: potential NULL/IS_ERR bug 'event'
> net/xfrm/xfrm_policy.c:2785 xfrm_policy_queue_process() error: potential NULL/IS_ERR bug 'dst'
> net/xfrm/xfrm_interface.c:282 xfrmi_xmit2() error: potential NULL/IS_ERR bug 'dst'
> net/ipv6/netfilter/nf_reject_ipv6.c:327 nf_send_reset6() error: potential NULL/IS_ERR bug 'dst'
> net/ipv6/ip6_tunnel.c:1161 ip6_tnl_xmit() error: potential NULL/IS_ERR bug 'dst'
> net/ipv6/ndisc.c:505 ndisc_send_skb() error: potential NULL/IS_ERR bug 'dst'
> security/selinux/hooks.c:3157 selinux_inode_follow_link() error: potential NULL/IS_ERR bug 'isec'
> security/selinux/hooks.c:3212 selinux_inode_permission() error: potential NULL/IS_ERR bug 'isec'
> 
> regards,
> dan carpenter