Hello,

syzbot found the following issue on:

HEAD commit: a41a877bc12d Merge branch 'for-next/fixes' into for-kernelci git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci console output: https://syzkaller.appspot.com/x/log.txt?x=17ae17bd080000 kernel config: https://syzkaller.appspot.com/x/.config?x=5cea15779c42821c dashboard link: https://syzkaller.appspot.com/bug?extid=c512687fff9d22327436 compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 userspace arch: arm64 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e8fee5080000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b6bf13080000

IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+c512687fff9d22327436@syzkaller.appspotmail.com

------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 3029 at lib/refcount.c:28 refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28 Modules linked in: CPU: 0 PID: 3029 Comm: syz-executor717 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28 lr : refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28 sp : ffff80001200baa0 x29: ffff80001200baa0 x28: 00000000000a201d x27: 0000000000002000 x26: dead000000000100 x25: 0000000000000000 x24: 0000000000000001 x23: 0000000000000001 x22: 0000000000000000 x21: 0000000000000000 x20: 0000000000000003 x19: ffff80000d937000 x18: 00000000000000c0 x17: ffff80000dd7a698 x16: ffff80000dbb8658 x15: ffff0000c10a4f80 x14: 0000000000000000 x13: 00000000ffffffff x12: ffff0000c10a4f80 x11: ff808000081c39dc x10: 0000000000000000 x9 : 9016e5cf66052a00 x8 : 9016e5cf66052a00 x7 : ffff800008197c8c x6 : 0000000000000000 x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000100000000 x0 : 0000000000000026 Call trace: refcount_warn_saturate+0x1a0/0x1c8 lib/refcount.c:28 __refcount_sub_and_test include/linux/refcount.h:283 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] kref_put include/linux/kref.h:64 [inline] __drm_gem_object_put include/drm/drm_gem.h:381 [inline] drm_gem_object_put include/drm/drm_gem.h:394 [inline] drm_gem_object_handle_put_unlocked+0x178/0x190 drivers/gpu/drm/drm_gem.c:240 drm_gem_object_release_handle+0x90/0xa8 drivers/gpu/drm/drm_gem.c:259 idr_for_each+0xf0/0x174 lib/idr.c:208 drm_gem_release+0x30/0x48 drivers/gpu/drm/drm_gem.c:932 drm_file_free+0x220/0x2cc drivers/gpu/drm/drm_file.c:281 drm_close_helper drivers/gpu/drm/drm_file.c:308 [inline] drm_release+0x108/0x22c drivers/gpu/drm/drm_file.c:495 __fput+0x198/0x3bc fs/file_table.c:320 ____fput+0x20/0x30 fs/file_table.c:353 task_work_run+0xc4/0x208 kernel/task_work.c:177 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0x26c/0xbb8 kernel/exit.c:795 do_group_exit+0x60/0xe8 kernel/exit.c:925 __do_sys_exit_group kernel/exit.c:936 [inline] __se_sys_exit_group kernel/exit.c:934 [inline] __wake_up_parent+0x0/0x40 kernel/exit.c:934 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall arch/arm64/kernel/syscall.c:52 [inline] el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x48/0x154 arch/arm64/kernel/syscall.c:206 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:624 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642 el0t_64_sync+0x18c/0x190 irq event stamp: 12698 hardirqs last enabled at (12697): [<ffff8000081c1c48>] __up_console_sem+0xb0/0xfc kernel/printk/printk.c:264 hardirqs last disabled at (12698): [<ffff80000bffe9cc>] el1_dbg+0x24/0x5c arch/arm64/kernel/entry-common.c:395 softirqs last enabled at (12442): [<ffff8000080102e4>] _stext+0x2e4/0x37c softirqs last disabled at (12417): [<ffff800008104658>] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline] softirqs last disabled at (12417): [<ffff800008104658>] invoke_softirq+0x70/0xbc kernel/softirq.c:452 ---[ end trace 0000000000000000 ]---

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