CVE-2025-21688: In the Linux kernel, the following vulnerability has been resolved:  drm/v3d: Assign job pointer to NULL before signaling the fence  In commit e4b5ccd392b9 ("drm/v3d: Ensure job pointer is set to NULL after job completion"), we introduced a change to assign the job pointer to NULL after completing a job, indicating job completion.  However, this approach created a race condition between the DRM scheduler workqueue and the IRQ execution thread. As soon as the fence is signaled in the IRQ execution thread, a new job starts to be executed. This results in a race condition where the IRQ execution thread sets the job pointer to NULL simultaneously as the `run_job()` function assigns a new job to the pointer.  This race condition can lead to a NULL pointer dereference if the IRQ execution thread sets the job pointer to NULL after `run_job()` assigns it to the new job. When the new job completes and the GPU emits an interrupt, `v3d_irq()` is triggered, potentially causing a crash.  [  466.310099] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000c0 [  466.318928] Mem abort info: [  466.321723]   ESR = 0x0000000096000005 [  466.325479]   EC = 0x25: DABT (current EL), IL = 32 bits [  466.330807]   SET = 0, FnV = 0 [  466.333864]   EA = 0, S1PTW = 0 [  466.337010]   FSC = 0x05: level 1 translation fault [  466.341900] Data abort info: [  466.344783]   ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 [  466.350285]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [  466.355350]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [  466.360677] user pgtable: 4k pages, 39-bit VAs, pgdp=0000000089772000 [  466.367140] [00000000000000c0] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 [  466.375875] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP [  466.382163] Modules linked in: rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device algif_hash algif_skcipher af_alg bnep binfmt_misc vc4 snd_soc_hdmi_codec drm_display_helper cec brcmfmac_wcc spidev rpivid_hevc(C) drm_client_lib brcmfmac hci_uart drm_dma_helper pisp_be btbcm brcmutil snd_soc_core aes_ce_blk v4l2_mem2mem bluetooth aes_ce_cipher snd_compress videobuf2_dma_contig ghash_ce cfg80211 gf128mul snd_pcm_dmaengine videobuf2_memops ecdh_generic sha2_ce ecc videobuf2_v4l2 snd_pcm v3d sha256_arm64 rfkill videodev snd_timer sha1_ce libaes gpu_sched snd videobuf2_common sha1_generic drm_shmem_helper mc rp1_pio drm_kms_helper raspberrypi_hwmon spi_bcm2835 gpio_keys i2c_brcmstb rp1 raspberrypi_gpiomem rp1_mailbox rp1_adc nvmem_rmem uio_pdrv_genirq uio i2c_dev drm ledtrig_pattern drm_panel_orientation_quirks backlight fuse dm_mod ip_tables x_tables ipv6 [  466.458429] CPU: 0 UID: 1000 PID: 2008 Comm: chromium Tainted: G         C         6.13.0-v8+ #18 [  466.467336] Tainted: [C]=CRAP [  466.470306] Hardware name: Raspberry Pi 5 Model B Rev 1.0 (DT) [  466.476157] pstate: 404000c9 (nZcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [  466.483143] pc : v3d_irq+0x118/0x2e0 [v3d] [  466.487258] lr : __handle_irq_event_percpu+0x60/0x228 [  466.492327] sp : ffffffc080003ea0 [  466.495646] x29: ffffffc080003ea0 x28: ffffff80c0c94200 x27: 0000000000000000 [  466.502807] x26: ffffffd08dd81d7b x25: ffffff80c0c94200 x24: ffffff8003bdc200 [  466.509969] x23: 0000000000000001 x22: 00000000000000a7 x21: 0000000000000000 [  466.517130] x20: ffffff8041bb0000 x19: 0000000000000001 x18: 0000000000000000 [  466.524291] x17: ffffffafadfb0000 x16: ffffffc080000000 x15: 0000000000000000 [  466.531452] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [  466.538613] x11: 0000000000000000 x10: 0000000000000000 x9 : ffffffd08c527eb0 [  466.545777] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000 [  466.552941] x5 : ffffffd08c4100d0 x4 : ffffffafadfb0000 x3 : ffffffc080003f70 [  466.560102] x2 : ffffffc0829e8058 x1 : 0000000000000001 x0 : 0000000000000000 [  466.567263] Call trace: [  466.569711]  v3d_irq+0x118/0x2e0 [v3d] (P) [  466. ---truncated---