> > From: Zqiang <qiang.zhang1211@xxxxxxxxx> > > [ Upstream commit 643445531829d89dc5ddbe0c5ee4ff8f84ce8687 ] > > Currently, for UNBOUND wq, if the apply_wqattrs_prepare() return error, > the apply_wqattr_cleanup() will be called and use the pwq_release_worker > kthread to release resources asynchronously. however, the kfree(wq) is > invoked directly in failure path of alloc_workqueue(), if the kfree(wq) > has been executed and when the pwq_release_workfn() accesses wq, this > leads to the following scenario: > > BUG: KASAN: slab-use-after-free in pwq_release_workfn+0x339/0x380 kernel/workqueue.c:4124 > Read of size 4 at addr ffff888027b831c0 by task pool_workqueue_/3 > > CPU: 0 PID: 3 Comm: pool_workqueue_ Not tainted 6.5.0-rc7-next-20230825-syzkaller #0 > Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 > print_address_description mm/kasan/report.c:364 [inline] > print_report+0xc4/0x620 mm/kasan/report.c:475 > kasan_report+0xda/0x110 mm/kasan/report.c:588 > pwq_release_workfn+0x339/0x380 kernel/workqueue.c:4124 > kthread_worker_fn+0x2fc/0xa80 kernel/kthread.c:823 > kthread+0x33a/0x430 kernel/kthread.c:388 > ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 > </TASK> > > Allocated by task 5054: > kasan_save_stack+0x33/0x50 mm/kasan/common.c:45 > kasan_set_track+0x25/0x30 mm/kasan/common.c:52 > ____kasan_kmalloc mm/kasan/common.c:374 [inline] > __kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383 > kmalloc include/linux/slab.h:599 [inline] > kzalloc include/linux/slab.h:720 [inline] > alloc_workqueue+0x16f/0x1490 kernel/workqueue.c:4684 > kvm_mmu_init_tdp_mmu+0x23/0x100 arch/x86/kvm/mmu/tdp_mmu.c:19 > kvm_mmu_init_vm+0x248/0x2e0 arch/x86/kvm/mmu/mmu.c:6180 > kvm_arch_init_vm+0x39/0x720 arch/x86/kvm/x86.c:12311 > kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1222 [inline] > kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:5089 [inline] > kvm_dev_ioctl+0xa31/0x1c20 arch/x86/kvm/../../../virt/kvm/kvm_main.c:5131 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:871 [inline] > __se_sys_ioctl fs/ioctl.c:857 [inline] > __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Freed by task 5054: > kasan_save_stack+0x33/0x50 mm/kasan/common.c:45 > kasan_set_track+0x25/0x30 mm/kasan/common.c:52 > kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:522 > ____kasan_slab_free mm/kasan/common.c:236 [inline] > ____kasan_slab_free+0x15b/0x1b0 mm/kasan/common.c:200 > kasan_slab_free include/linux/kasan.h:164 [inline] > slab_free_hook mm/slub.c:1800 [inline] > slab_free_freelist_hook+0x114/0x1e0 mm/slub.c:1826 > slab_free mm/slub.c:3809 [inline] > __kmem_cache_free+0xb8/0x2f0 mm/slub.c:3822 > alloc_workqueue+0xe76/0x1490 kernel/workqueue.c:4746 > kvm_mmu_init_tdp_mmu+0x23/0x100 arch/x86/kvm/mmu/tdp_mmu.c:19 > kvm_mmu_init_vm+0x248/0x2e0 arch/x86/kvm/mmu/mmu.c:6180 > kvm_arch_init_vm+0x39/0x720 arch/x86/kvm/x86.c:12311 > kvm_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1222 [inline] > kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:5089 [inline] > kvm_dev_ioctl+0xa31/0x1c20 arch/x86/kvm/../../../virt/kvm/kvm_main.c:5131 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:871 [inline] > __se_sys_ioctl fs/ioctl.c:857 [inline] > __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > This commit therefore flush pwq_release_worker in the alloc_and_link_pwqs() > before invoke kfree(wq). > > Reported-by: syzbot+60db9f652c92d5bacba4@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://syzkaller.appspot.com/bug?extid=60db9f652c92d5bacba4 > Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx> > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > kernel/workqueue.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index e51ab3d4765eb..a0045c159a0e1 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -4567,6 +4567,12 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq) > } > cpus_read_unlock(); > > + /* for unbound pwq, flush the pwq_release_worker ensures that the > + * pwq_release_workfn() completes before calling kfree(wq). > + */ > + if (ret) > + kthread_flush_worker(pwq_release_worker); > + > return ret; > } > Hello Sasha, the pwq_release_worker only exists in the V6.6 kernel, the previous versions of kernels do not use this mechanism. Thanks Zqiang > > -- > 2.40.1 >
