If drm_sysfs_minor_alloc() fail in drm_minor_alloc() we can end up freeing invalid minor->kdev pointer and drm_minor_alloc_release() will crash like below: RIP: 0010:kobject_put+0x19/0x1c0 RSP: 0018:ffffbc7001637c38 EFLAGS: 00010282 RAX: ffffffffa8d6deb0 RBX: 00000000ffffffff RCX: ffff9cb5912d4540 RDX: ffffffffa9c45ec5 RSI: ffff9cb5902f2b68 RDI: fffffffffffffff4 RBP: fffffffffffffff4 R08: ffffffffa9c40dec R09: 0000000000000008 R10: ffffffffaa81f7d2 R11: 00000000aa81f7ca R12: ffff9cb5912d4540 R13: ffff9cb5912d4540 R14: dead000000000122 R15: dead000000000100 FS: 00007f56b06e6740(0000) GS:ffff9cb728b40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000030 CR3: 000000011285b004 CR4: 0000000000170ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400 Call Trace: <TASK> drm_minor_alloc_release+0x19/0x50 drm_managed_release+0xab/0x150 drm_dev_init+0x21f/0x2f0 __devm_drm_dev_alloc+0x3c/0xa0 ivpu_probe+0x59/0x797 [intel_vpu 127058409b05eb2f99dcdecd3330bee28d6b3e76] pci_device_probe+0xa4/0x160 really_probe+0x164/0x340 __driver_probe_device+0x10d/0x190 device_driver_attach+0x26/0x50 bind_store+0x9f/0x120 kernfs_fop_write_iter+0x12d/0x1c0 new_sync_write+0x106/0x180 vfs_write+0x216/0x2a0 ksys_write+0x65/0xe0 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Fix this crash by checking minor->kdev when freeing. Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@xxxxxxxxxxxxxxx> --- drivers/gpu/drm/drm_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 8214a0b1ab7f..e3a1243dd2ae 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -102,7 +102,8 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data) WARN_ON(dev != minor->dev); - put_device(minor->kdev); + if (!IS_ERR(minor->kdev)) + put_device(minor->kdev); spin_lock_irqsave(&drm_minor_lock, flags); idr_remove(&drm_minors_idr, minor->index); -- 2.25.1
