dmsg:

[    1.538385] [drm:i915_stolen_to_physical] *ERROR* conflict detected with stolen region: [0xbf800000 - 0xbff80000]

[  210.093951] vainfo[4873]: segfault at 28 ip 00007fc567ddbe47 sp 00007fff8cf2fd20 error 4 in i965_drv_video.so[7fc567d9a000+16e000]
[  246.005126] vainfo[4895]: segfault at 28 ip 00007f7dd1a70e47 sp 00007fff80ef98d0 error 4 in i965_drv_video.so[7f7dd1a2f000+16e000]
[  436.935647] vainfo[5133]: segfault at 28 ip 00007f542dac9e47 sp 00007fff8f641d80 error 4 in i965_drv_video.so[7f542da88000+16e000]
[ 1350.184865] vainfo[6523]: segfault at 28 ip 00007f6c28717e47 sp 00007fff18756be0 error 4 in i965_drv_video.so[7f6c286d6000+16e000]

[ 1704.395466] vlc[7096]: segfault at 28 ip 00007f6774813e47 sp 00007f6777ffe5d0 error 4 in i965_drv_video.so[7f67747d2000+16e000]
[ 1724.526088] vlc[7140]: segfault at 28 ip 00007f6cb0aa0e47 sp 00007f6cb48965d0 error 4 in i965_drv_video.so[7f6cb0a5f000+16e000]
[ 1743.371222] vlc[7177]: segfault at 28 ip 00007fc5e98a9e47 sp 00007fc5fb5de5d0 error 4 in i965_drv_video.so[7fc5e9868000+16e000]
[ 2098.384616] ------------[ cut here ]------------
[ 2098.384707] WARNING: CPU: 1 PID: 1649 at drivers/gpu/drm/i915/i915_gem.c:4515 i915_gem_free_object+0x396/0x3c0 [i915]()
[ 2098.384713] Modules linked in: hidp rfcomm ccm fuse xt_physdev br_netfilter bridge stp llc nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack bnep arc4 iwl4965 iwlegacy coretemp mac80211 iTCO_wdt iTCO_vendor_support kvm_intel uvcvideo videobuf2_vmalloc kvm videobuf2_core btusb videobuf2_memops v4l2_common snd_hda_codec_si3054 bluetooth snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel videodev snd_hda_controller snd_hda_codec media cfg80211 snd_hwdep joydev snd_seq serio_raw r592 memstick lpc_ich mfd_core snd_seq_device snd_pcm snd_timer snd shpchp soundcore tpm_infineon tpm_tis tpm asus_laptop sparse_keymap rfkill input_polldev phc_intel(OE) nfsd auth_rpcgss nfs_acl lockd grace sunrpc binfmt_misc dm_crypt sdhci_pci sdhci firewire_ohci ata_generic pata_acpi firewire_core atl1 mmc_core
[ 2098.384836]  crc_itu_t mii i915 i2c_algo_bit video drm_kms_helper drm
[ 2098.384856] CPU: 1 PID: 1649 Comm: Xorg.bin Tainted: G           OE  3.18.6-200.fc21.x86_64 #1
[ 2098.384862] Hardware name: ASUSTeK Computer Inc.         F3E                 /F3E       , BIOS 305     07/21/2008
[ 2098.384867]  0000000000000000 000000007679a1c0 ffff880135bdbc68 ffffffff8175e486
[ 2098.384876]  0000000000000000 0000000000000000 ffff880135bdbca8 ffffffff810991b1
[ 2098.384884]  ffff88003ba4ac58 ffff88010f48a700 ffff88010f48a758 ffff88010f48a7c0
[ 2098.384893] Call Trace:
[ 2098.384907]  [<ffffffff8175e486>] dump_stack+0x46/0x58
[ 2098.384919]  [<ffffffff810991b1>] warn_slowpath_common+0x81/0xa0
[ 2098.384927]  [<ffffffff810992ca>] warn_slowpath_null+0x1a/0x20
[ 2098.384975]  [<ffffffffa00a4ae6>] i915_gem_free_object+0x396/0x3c0 [i915]
[ 2098.385006]  [<ffffffffa00043f7>] drm_gem_object_free+0x27/0x40 [drm]
[ 2098.385066]  [<ffffffffa0004980>] drm_gem_object_handle_unreference_unlocked+0x120/0x130 [drm]
[ 2098.385103]  [<ffffffffa0004a36>] drm_gem_handle_delete+0xa6/0x100 [drm]
[ 2098.385142]  [<ffffffffa00050d5>] drm_gem_close_ioctl+0x25/0x30 [drm]
[ 2098.385179]  [<ffffffffa0005aaf>] drm_ioctl+0x1df/0x680 [drm]
[ 2098.385190]  [<ffffffff811c5044>] ? tlb_flush_mmu_free+0x34/0x60
[ 2098.385224]  [<ffffffffa000b1e0>] ? drm_vm_close_locked+0x80/0xb0 [drm]
[ 2098.385234]  [<ffffffff811f562e>] ? kfree+0x14e/0x160
[ 2098.385243]  [<ffffffff8122a110>] do_vfs_ioctl+0x2d0/0x4b0
[ 2098.385254]  [<ffffffff8113ab64>] ? __audit_syscall_entry+0xc4/0x120
[ 2098.385264]  [<ffffffff81021d9c>] ? do_audit_syscall_entry+0x6c/0x70
[ 2098.385271]  [<ffffffff8122a371>] SyS_ioctl+0x81/0xa0
[ 2098.385279]  [<ffffffff8113adb6>] ? __audit_syscall_exit+0x1f6/0x2a0
[ 2098.385300]  [<ffffffff817651e9>] system_call_fastpath+0x12/0x17
[ 2098.385312] ---[ end trace 02ec9f46ad6f74bc ]---

Removing libvdpau-va-gl and libva-intel-driver, solves my problem with vlc and kodi.

It seems vaai and vdpau is not compatible with my graphics card, and for some reason the version of the driver in F21 just crashes anything that tries to use it, so removing the driver or disabling it's use on vlc and kodi solves my problem.

You shouldn't have a crash even if your hardware is not supported.
What is the output of vainfo ?
I don't understand why you are reporting two intel VGA devices, which hardware is that ?

You might need to report the issue to Intel directly using bugzilla.freedesktop.org. While doing so, please provide the link for reference.

After upgrade to Fedora 22 the problem doesn't happen anymore.

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