bisecting fixing commit since 4abf26854aade9732a215a168205fa9fecd6149a building syzkaller on 99917735b6a974a09d3833c34b3d4a8b8198522d testing commit 4abf26854aade9732a215a168205fa9fecd6149a with gcc (GCC) 8.4.1 20210217 kernel signature: fcd7e4816fc5b689fc09bffe0a311ee33ede91788528ad8c515da61565291d00 all runs: crashed: KASAN: use-after-free Read in drm_getunique testing current HEAD 78fec1611cbf7b0bdaddfdbf174a3a2463663bff testing commit 78fec1611cbf7b0bdaddfdbf174a3a2463663bff with gcc (GCC) 8.4.1 20210217 kernel signature: 6c9b64835c7c45b80fe1504c77eadac0cd7917a280149838c30a7638f37a2050 all runs: crashed: KASAN: use-after-free Read in drm_getunique revisions tested: 2, total time: 22m2.665602914s (build: 15m9.337411035s, test: 6m31.64277997s) the crash still happens on HEAD commit msg: Linux 4.19.183 crash: KASAN: use-after-free Read in drm_getunique IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready ================================================================== BUG: KASAN: use-after-free in drm_getunique+0x19e/0x250 drivers/gpu/drm/drm_ioctl.c:118 Read of size 4 at addr ffff8880a95f45d8 by task syz-executor.0/10564 CPU: 1 PID: 10564 Comm: syz-executor.0 Not tainted 4.19.183-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report mm/kasan/report.c:412 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 drm_getunique+0x19e/0x250 drivers/gpu/drm/drm_ioctl.c:118 drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:757 drm_ioctl+0x6a9/0xae0 drivers/gpu/drm/drm_ioctl.c:857 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4659b9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f5d87f38188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bfe8 RCX: 00000000004659b9 RDX: 0000000020000180 RSI: 00000000c0145401 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfe8 R13: 00007ffffc0da93f R14: 00007f5d87f38300 R15: 0000000000022000 Allocated by task 10552: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kmem_cache_alloc_trace+0x152/0x3a0 mm/slab.c:3625 kmalloc include/linux/slab.h:515 [inline] kzalloc include/linux/slab.h:709 [inline] drm_master_create+0x42/0x550 drivers/gpu/drm/drm_auth.c:101 drm_new_set_master+0xf8/0x350 drivers/gpu/drm/drm_auth.c:147 drm_master_open+0xd6/0x110 drivers/gpu/drm/drm_auth.c:257 drm_open_helper drivers/gpu/drm/drm_file.c:376 [inline] drm_open+0x28f/0x6e0 drivers/gpu/drm/drm_file.c:316 drm_stub_open+0x260/0x430 drivers/gpu/drm/drm_drv.c:950 chrdev_open+0x1ed/0x5c0 fs/char_dev.c:423 do_dentry_open+0x3f1/0x1020 fs/open.c:796 vfs_open+0x9a/0xc0 fs/open.c:902 do_last fs/namei.c:3421 [inline] path_openat+0x925/0x2900 fs/namei.c:3537 do_filp_open+0x177/0x250 fs/namei.c:3567 do_sys_open+0x1dc/0x350 fs/open.c:1085 __do_sys_openat fs/open.c:1112 [inline] __se_sys_openat fs/open.c:1106 [inline] __x64_sys_openat+0x98/0xf0 fs/open.c:1106 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 10552: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 drm_master_destroy drivers/gpu/drm/drm_auth.c:356 [inline] kref_put include/linux/kref.h:70 [inline] drm_master_put+0x172/0x200 drivers/gpu/drm/drm_auth.c:367 drm_new_set_master+0x1c9/0x350 drivers/gpu/drm/drm_auth.c:166 drm_setmaster_ioctl+0x10c/0x190 drivers/gpu/drm/drm_auth.c:199 drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:757 drm_ioctl+0x6a9/0xae0 drivers/gpu/drm/drm_ioctl.c:857 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8880a95f45c0 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 24 bytes inside of 512-byte region [ffff8880a95f45c0, ffff8880a95f47c0) The buggy address belongs to the page: page:ffffea0002a57d00 count:1 mapcount:0 mapping:ffff88813bff6940 index:0x0 flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffffea000252d808 ffffea0002716608 ffff88813bff6940 raw: 0000000000000000 ffff8880a95f40c0 0000000100000006 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a95f4480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a95f4500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >ffff8880a95f4580: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8880a95f4600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a95f4680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================