bisecting fixing commit since b172b44fcb1771e083aad806fa96f3f60e2ddfac building syzkaller on 064c9eb76747f86a8270c8cfc3766316ebdf3167 testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: ce597556127acbb884c23a645b741758cfeb8add43a9a342366b2b6ab8da66e1 all runs: crashed: KASAN: use-after-free Read in snd_mixer_oss_get_volume1 testing current HEAD 6db10b4d5efdc38ff06dfdde28dc5477f754b0bd testing commit 6db10b4d5efdc38ff06dfdde28dc5477f754b0bd compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 0b7b9fee83d2f5b46645584f73914a400ae746336491ae780cd898f80c678140 all runs: crashed: KASAN: use-after-free Read in snd_mixer_oss_get_volume1 revisions tested: 2, total time: 26m39.062774541s (build: 19m28.956178936s, test: 6m43.393284775s) the crash still happens on HEAD commit msg: Linux 4.19.209 crash: KASAN: use-after-free Read in snd_mixer_oss_get_volume1 Bluetooth: hci3: command 0x0419 tx timeout Bluetooth: hci4: command 0x0419 tx timeout Bluetooth: hci5: command 0x0419 tx timeout Bluetooth: hci1: command 0x0419 tx timeout ================================================================== BUG: KASAN: use-after-free in snd_mixer_oss_get_volume1+0x4ba/0x570 sound/core/oss/mixer_oss.c:608 Read of size 4 at addr ffff8880a9ace584 by task syz-executor.1/10491 CPU: 1 PID: 10491 Comm: syz-executor.1 Not tainted 4.19.209-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 snd_mixer_oss_get_volume1+0x4ba/0x570 sound/core/oss/mixer_oss.c:608 snd_mixer_oss_get_volume sound/core/oss/mixer_oss.c:272 [inline] snd_mixer_oss_ioctl1+0x1e5/0x1730 sound/core/oss/mixer_oss.c:372 snd_mixer_oss_ioctl+0x36/0x60 sound/core/oss/mixer_oss.c:382 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: 0033:0x4665f9 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:00007fbee7c01188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665f9 RDX: 0000000000000000 RSI: 0000000080254d18 RDI: 0000000000000003 RBP: 00000000004bfcc4 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80 R13: 00007ffe777d57ef R14: 00007fbee7c01300 R15: 0000000000022000 Allocated by task 10479: 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] snd_mixer_oss_build_input+0x56f/0xc70 sound/core/oss/mixer_oss.c:1092 snd_mixer_oss_proc_write+0x30c/0x4a0 sound/core/oss/mixer_oss.c:1232 snd_info_text_entry_release+0xe3/0x240 sound/core/info.c:425 close_pdeo.part.0+0xd8/0x2e0 fs/proc/inode.c:176 close_pdeo+0xf6/0x150 fs/proc/inode.c:168 proc_reg_release+0xff/0x170 fs/proc/inode.c:395 __fput+0x249/0x7f0 fs/file_table.c:278 ____fput+0x9/0x10 fs/file_table.c:309 task_work_run+0x108/0x180 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x185/0x1e0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 10488: 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 snd_mixer_oss_slot_free+0xcf/0x110 sound/core/oss/mixer_oss.c:955 mixer_slot_clear+0x53/0xa0 sound/core/oss/mixer_oss.c:963 snd_mixer_oss_build_input+0x702/0xc70 sound/core/oss/mixer_oss.c:1100 snd_mixer_oss_proc_write+0x30c/0x4a0 sound/core/oss/mixer_oss.c:1232 snd_info_text_entry_release+0xe3/0x240 sound/core/info.c:425 close_pdeo.part.0+0xd8/0x2e0 fs/proc/inode.c:176 close_pdeo+0xf6/0x150 fs/proc/inode.c:168 proc_reg_release+0xff/0x170 fs/proc/inode.c:395 __fput+0x249/0x7f0 fs/file_table.c:278 ____fput+0x9/0x10 fs/file_table.c:309 task_work_run+0x108/0x180 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x185/0x1e0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8880a9ace580 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 4 bytes inside of 96-byte region [ffff8880a9ace580, ffff8880a9ace5e0) The buggy address belongs to the page: page:ffffea0002a6b380 count:1 mapcount:0 mapping:ffff88813bff64c0 index:0x0 flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffffea0002a53308 ffffea0002a40608 ffff88813bff64c0 raw: 0000000000000000 ffff8880a9ace000 0000000100000020 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880a9ace480: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff8880a9ace500: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >ffff8880a9ace580: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ^ ffff8880a9ace600: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff8880a9ace680: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ==================================================================