bisecting fixing commit since 9a2dc0e6c531d595bcdf2c66d0be131679bd02df building syzkaller on 1ba81399e2d03b53a7e631c4ab05f25af1fb1911 testing commit 9a2dc0e6c531d595bcdf2c66d0be131679bd02df compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 9f58c67fbfe96a1aca4121ba9b39199fb742c925af1c69982f0850a8e083f5dd run #0: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #1: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #2: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #3: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #4: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #5: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #6: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #7: crashed: WARNING in mutex_destroy run #8: crashed: general protection fault in vgem_fence_attach_ioctl run #9: crashed: general protection fault in vgem_fence_attach_ioctl run #10: crashed: WARNING in mutex_destroy run #11: crashed: general protection fault in vgem_fence_attach_ioctl run #12: crashed: general protection fault in vgem_fence_attach_ioctl run #13: crashed: WARNING in mutex_destroy run #14: crashed: general protection fault in vgem_fence_attach_ioctl run #15: crashed: general protection fault in vgem_fence_attach_ioctl run #16: crashed: general protection fault in vgem_fence_attach_ioctl run #17: crashed: general protection fault in vgem_fence_attach_ioctl run #18: crashed: general protection fault in vgem_fence_attach_ioctl run #19: crashed: WARNING in mutex_destroy testing current HEAD 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 testing commit 59456c9cc40c8f75b5a7efa0fe1f211d9c6fcaf1 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 406ad073a493452a0997714cddd40df3f7b586dbbf43f7aa642ce33b45f23282 run #0: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #1: crashed: KASAN: use-after-free Read in vgem_gem_dumb_create run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK reproducer seems to be flaky Reproducer flagged being flaky revisions tested: 2, total time: 42m32.972261157s (build: 21m22.632427063s, test: 20m43.970583649s) the crash still happens on HEAD commit msg: Linux 4.19.204 crash: KASAN: use-after-free Read in vgem_gem_dumb_create ================================================================== BUG: KASAN: use-after-free in vgem_gem_dumb_create+0x1d2/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:214 Read of size 8 at addr ffff888096133e40 by task syz-executor.0/22075 CPU: 0 PID: 22075 Comm: syz-executor.0 Not tainted 4.19.204-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_load8_noabort+0x14/0x20 mm/kasan/report.c:433 vgem_gem_dumb_create+0x1d2/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:214 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:758 drm_ioctl+0x6be/0xaf0 drivers/gpu/drm/drm_ioctl.c:861 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: 0033:0x4665d9 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:00007f04fb110188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9 RDX: 00000000200000c0 RSI: 00000000c02064b2 RDI: 0000000000000003 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007ffd774a2bbf R14: 00007f04fb110300 R15: 0000000000022000 Allocated by task 22075: 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] __vgem_gem_create+0x47/0xd0 drivers/gpu/drm/vgem/vgem_drv.c:158 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:187 [inline] vgem_gem_dumb_create+0xba/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:210 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:758 drm_ioctl+0x6be/0xaf0 drivers/gpu/drm/drm_ioctl.c:861 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 Freed by task 22075: 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 vgem_gem_free_object+0xa7/0xd0 drivers/gpu/drm/vgem/vgem_drv.c:61 drm_gem_object_free+0x89/0x1a0 drivers/gpu/drm/drm_gem.c:837 kref_put include/linux/kref.h:70 [inline] drm_gem_object_put.part.3+0x16/0x20 drivers/gpu/drm/drm_gem.c:893 drm_gem_object_put_unlocked+0x91/0x120 drivers/gpu/drm/drm_gem.c:865 vgem_gem_create drivers/gpu/drm/vgem/vgem_drv.c:192 [inline] vgem_gem_dumb_create+0xed/0x1f0 drivers/gpu/drm/vgem/vgem_drv.c:210 drm_mode_create_dumb+0x1ea/0x2b0 drivers/gpu/drm/drm_dumb_buffers.c:92 drm_mode_create_dumb_ioctl+0x9/0x10 drivers/gpu/drm/drm_dumb_buffers.c:98 drm_ioctl_kernel+0x1b7/0x240 drivers/gpu/drm/drm_ioctl.c:758 drm_ioctl+0x6be/0xaf0 drivers/gpu/drm/drm_ioctl.c:861 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 ffff888096133d40 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 256 bytes inside of 512-byte region [ffff888096133d40, ffff888096133f40) The buggy address belongs to the page: page:ffffea0002584cc0 count:1 mapcount:0 mapping:ffff88813bff6940 index:0xffff888096133840 flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffffea0002832d88 ffffea00026df208 ffff88813bff6940 raw: ffff888096133840 ffff8880961330c0 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888096133d00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff888096133d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888096133e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888096133e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888096133f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ==================================================================