Re: [PATCH] media: v4l2-compat-ioctl32: don't oops on overlay

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hello,

On Wednesday, 28 March 2018 23:16:08 EEST Sakari Ailus wrote:
> On Wed, Mar 28, 2018 at 02:59:22PM -0300, Mauro Carvalho Chehab wrote:
> > At put_v4l2_window32(), it tries to access kp->clips. However,
> > kp points to an userspace pointer. So, it should be obtained
> > 
> > via get_user(), otherwise it can OOPS:
> >  vivid-000: ==================  END STATUS  ==================
> >  BUG: unable to handle kernel paging request at 00000000fffb18e0
> >  IP: [<ffffffffc05468d9>] __put_v4l2_format32+0x169/0x220 [videodev]
> >  PGD 3f5776067 PUD 3f576f067 PMD 3f5769067 PTE 800000042548f067
> >  Oops: 0001 [#1] SMP
> >  Modules linked in: vivid videobuf2_vmalloc videobuf2_memops
> >  v4l2_dv_timings videobuf2_core v4l2_common videodev media xt_CHECKSUM
> >  iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat
> >  nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack
> >  nf_conntrack tun bridge stp llc ebtable_filter ebtables ip6table_filter
> >  ip6_tables bluetooth rfkill binfmt_misc snd_hda_codec_hdmi i915
> >  snd_hda_intel snd_hda_controller snd_hda_codec intel_rapl
> >  x86_pkg_temp_thermal snd_hwdep intel_powerclamp snd_pcm coretemp
> >  snd_seq_midi kvm_intel kvm snd_seq_midi_event snd_rawmidi i2c_algo_bit
> >  drm_kms_helper snd_seq drm crct10dif_pclmul e1000e snd_seq_device
> >  crc32_pclmul snd_timer ghash_clmulni_intel snd mei_me mei ptp pps_core
> >  soundcore lpc_ich video crc32c_intel [last unloaded: media] CPU: 2 PID:
> >  28332 Comm: v4l2-compliance Not tainted 3.18.102+ #107 Hardware name:   
> >                /NUC5i7RYB, BIOS RYBDWi35.86A.0364.2017.0511.0949
> >  05/11/2017 task: ffff8804293f8000 ti: ffff8803f5640000 task.ti:
> >  ffff8803f5640000 RIP: 0010:[<ffffffffc05468d9>]  [<ffffffffc05468d9>]
> >  __put_v4l2_format32+0x169/0x220 [videodev] RSP: 0018:ffff8803f5643e28 
> >  EFLAGS: 00010246
> >  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000fffb1ab4
> >  RDX: 00000000fffb1a68 RSI: 00000000fffb18d8 RDI: 00000000fffb1aa8
> >  RBP: ffff8803f5643e48 R08: 0000000000000001 R09: ffff8803f54b0378
> >  R10: 0000000000000000 R11: 0000000000000168 R12: 00000000fffb18c0
> >  R13: 00000000fffb1a94 R14: 00000000fffb18c8 R15: 0000000000000000
> >  FS:  0000000000000000(0000) GS:ffff880456d00000(0063)
> >  knlGS:00000000f7100980 CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> >  CR2: 00000000fffb18e0 CR3: 00000003f552b000 CR4: 00000000003407e0
> >  
> >  Stack:
> >   00000000fffb1a94 00000000c0cc5640 0000000000000056 ffff8804274f3600
> >   ffff8803f5643ed0 ffffffffc0547e16 0000000000000003 ffff8803f5643eb0
> >   ffffffff81301460 ffff88009db44b01 ffff880441942520 ffff8800c0d05640
> >  
> >  Call Trace:
> >   [<ffffffffc0547e16>] v4l2_compat_ioctl32+0x12d6/0x1b1d [videodev]
> >   [<ffffffff81301460>] ? file_has_perm+0x70/0xc0
> >   [<ffffffff81252a2c>] compat_SyS_ioctl+0xec/0x1200
> >   [<ffffffff8173241a>] sysenter_dispatch+0x7/0x21
> >  
> >  Code: 00 00 48 8b 80 48 c0 ff ff 48 83 e8 38 49 39 c6 0f 87 2b ff ff ff
> >  49 8d 45 1c e8 a3 ce e3 c0 85 c0 0f 85 1a ff ff ff 41 8d 40 ff <4d> 8b
> >  64 24 20 41 89 d5 48 8d 44 40 03 4d 8d 34 c4 eb 15 0f 1f RIP 
> >  [<ffffffffc05468d9>] __put_v4l2_format32+0x169/0x220 [videodev] RSP
> >  <ffff8803f5643e28>
> >  CR2: 00000000fffb18e0
> > 
> > Tested with vivid driver on Kernel v3.18.102.
> > 
> > Same bug happens upstream too:
> >  BUG: KASAN: user-memory-access in __put_v4l2_format32+0x98/0x4d0
> >  [videodev]
> >  Read of size 8 at addr 00000000ffe48400 by task v4l2-compliance/8713
> >  
> >  CPU: 0 PID: 8713 Comm: v4l2-compliance Not tainted 4.16.0-rc4+ #108
> >  Hardware name:  /NUC5i7RYB, BIOS RYBDWi35.86A.0364.2017.0511.0949
> >  05/11/2017>  
> >  Call Trace:
> >   dump_stack+0x5c/0x7c
> >   kasan_report+0x164/0x380
> >   ? __put_v4l2_format32+0x98/0x4d0 [videodev]
> >   __put_v4l2_format32+0x98/0x4d0 [videodev]
> >   v4l2_compat_ioctl32+0x1aec/0x27a0 [videodev]
> >   ? __fsnotify_inode_delete+0x20/0x20
> >   ? __put_v4l2_format32+0x4d0/0x4d0 [videodev]
> >   compat_SyS_ioctl+0x646/0x14d0
> >   ? do_ioctl+0x30/0x30
> >   do_fast_syscall_32+0x191/0x3f4
> >   entry_SYSENTER_compat+0x6b/0x7a
> >  
> >  ==================================================================
> >  Disabling lock debugging due to kernel taint
> >  BUG: unable to handle kernel paging request at 00000000ffe48400
> >  IP: __put_v4l2_format32+0x98/0x4d0 [videodev]
> >  PGD 3a22fb067 P4D 3a22fb067 PUD 39b6f0067 PMD 39b6f1067 PTE
> >  80000003256af067 Oops: 0001 [#1] SMP KASAN
> >  Modules linked in: vivid videobuf2_vmalloc videobuf2_dma_contig
> >  videobuf2_memops v4l2_tpg v4l2_dv_timings videobuf2_v4l2
> >  videobuf2_common v4l2_common videodev xt_CHECKSUM iptable_mangle
> >  ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat
> >  nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack libcrc32c tun
> >  bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables
> >  bluetooth rfkill ecdh_generic binfmt_misc snd_hda_codec_hdmi intel_rapl
> >  x86_pkg_temp_thermal intel_powerclamp i915 coretemp snd_hda_intel
> >  snd_hda_codec kvm_intel snd_hwdep snd_hda_core kvm snd_pcm irqbypass
> >  crct10dif_pclmul crc32_pclmul snd_seq_midi ghash_clmulni_intel
> >  snd_seq_midi_event i2c_algo_bit intel_cstate snd_rawmidi intel_uncore
> >  snd_seq drm_kms_helper e1000e snd_seq_device snd_timer intel_rapl_perf>  
> >   drm ptp snd mei_me mei lpc_ich pps_core soundcore video crc32c_intel
> >  
> >  CPU: 0 PID: 8713 Comm: v4l2-compliance Tainted: G    B           
> >  4.16.0-rc4+ #108 Hardware name:  /NUC5i7RYB, BIOS
> >  RYBDWi35.86A.0364.2017.0511.0949 05/11/2017 RIP:
> >  0010:__put_v4l2_format32+0x98/0x4d0 [videodev]
> >  RSP: 0018:ffff8803b9be7d30 EFLAGS: 00010282
> >  RAX: 0000000000000000 RBX: ffff8803ac983e80 RCX: ffffffff8cd929f2
> >  RDX: 1ffffffff1d0a149 RSI: 0000000000000297 RDI: 0000000000000297
> >  RBP: 00000000ffe485c0 R08: fffffbfff1cf5123 R09: ffffffff8e7a8948
> >  R10: 0000000000000001 R11: fffffbfff1cf5122 R12: 00000000ffe483e0
> >  R13: 00000000ffe485c4 R14: ffff8803ac985918 R15: 00000000ffe483e8
> >  FS:  0000000000000000(0000) GS:ffff880407400000(0063)
> >  knlGS:00000000f7a46980 CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> >  CR2: 00000000ffe48400 CR3: 00000003a83f2003 CR4: 00000000003606f0
> >  
> >  Call Trace:
> >   v4l2_compat_ioctl32+0x1aec/0x27a0 [videodev]
> >   ? __fsnotify_inode_delete+0x20/0x20
> >   ? __put_v4l2_format32+0x4d0/0x4d0 [videodev]
> >   compat_SyS_ioctl+0x646/0x14d0
> >   ? do_ioctl+0x30/0x30
> >   do_fast_syscall_32+0x191/0x3f4
> >   entry_SYSENTER_compat+0x6b/0x7a
> >  
> >  Code: 4c 89 f7 4d 8d 7c 24 08 e8 e6 a4 69 cb 48 8b 83 98 1a 00 00 48 83
> >  e8 10 49 39 c7 0f 87 9d 01 00 00 49 8d 7c 24 20 e8 c8 a4 69 cb <4d> 8b
> >  74 24 20 4c 89 ef 4c 89 fe ba 10 00 00 00 e8 23 d9 08 cc RIP:
> >  __put_v4l2_format32+0x98/0x4d0 [videodev] RSP: ffff8803b9be7d30 CR2:
> >  00000000ffe48400
> > 
> > cc: stable@vger.kernel.org
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> > ---
> > 
> >  drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c index
> > 5198c9eeb348..4312935f1dfc 100644
> > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > @@ -101,7 +101,7 @@ static int get_v4l2_window32(struct v4l2_window __user
> > *kp,
> >  static int put_v4l2_window32(struct v4l2_window __user *kp,
> >  			     struct v4l2_window32 __user *up)
> >  {
> > -	struct v4l2_clip __user *kclips = kp->clips;
> > +	struct v4l2_clip __user *kclips;
> >  	struct v4l2_clip32 __user *uclips;
> >  	compat_caddr_t p;
> >  	u32 clipcount;
> > @@ -116,6 +116,8 @@ static int put_v4l2_window32(struct v4l2_window __user
> > *kp,
> >  	if (!clipcount)
> >  		return 0;
> > 
> > +	if (get_user(kclips, &kp->clips))
> > +		return -EFAULT;
> >  	if (get_user(p, &up->clips))
> >  		return -EFAULT;
> >  	uclips = compat_ptr(p);
> 
> Good find. I checked for similar problems elsewhere in the file but could
> not find any.
> 
> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>

Would it be useful to rename kp to something that doesn't imply the memory is 
kernel memory ? I was confused at first when reading this patch.

-- 
Regards,

Laurent Pinchart