On Fri, Mar 3, 2017 at 10:51 AM, Dmitry Vyukov <dvyu...@google.com> wrote: > Hello, > > I am hitting the following use-after-free reports while running > syzkaller fuzzer on commit c82be9d2244aacea9851c86f4fb74694c99cd874: > > ================================================================== > BUG: KASAN: use-after-free in ida_get_new_above+0x564/0x9b0 > lib/idr.c:295 at addr ffff880160ef3600 > Write of size 128 by task syz-executor1/1757 > CPU: 1 PID: 1757 Comm: syz-executor1 Not tainted 4.10.0+ #98 > Hardware name: Google Google Compute Engine/Google Compute Engine, > BIOS Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:15 [inline] > dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 > kasan_object_err+0x1c/0x70 mm/kasan/report.c:162 > print_address_description mm/kasan/report.c:200 [inline] > kasan_report_error mm/kasan/report.c:289 [inline] > kasan_report.part.2+0x1e5/0x4b0 mm/kasan/report.c:311 > kasan_report+0x21/0x30 mm/kasan/report.c:298 > check_memory_region_inline mm/kasan/kasan.c:315 [inline] > check_memory_region+0x139/0x190 mm/kasan/kasan.c:322 > memset+0x23/0x40 mm/kasan/kasan.c:340 > ida_get_new_above+0x564/0x9b0 lib/idr.c:295 > ida_get_new include/linux/idr.h:209 [inline] > proc_alloc_inum+0x97/0x1f0 fs/proc/generic.c:201 > proc_register+0x25/0x2f0 fs/proc/generic.c:338 > proc_create_data+0x100/0x190 fs/proc/generic.c:509 > proc_create include/linux/proc_fs.h:35 [inline] > ip_rt_do_proc_init+0x53/0x110 net/ipv4/route.c:382 > ops_init+0x10a/0x530 net/core/net_namespace.c:115 > setup_net+0x2ed/0x690 net/core/net_namespace.c:291 > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396 > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106 > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205 > SYSC_unshare kernel/fork.c:2281 [inline] > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > RIP: 0033:0x44fb79 > RSP: 002b:00007f1b66930b58 EFLAGS: 00000212 ORIG_RAX: 0000000000000110 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044fb79 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062020200 > RBP: 0000000062020200 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000212 R12: 00000000007082a0 > R13: 0000000000000004 R14: 0000000000000400 R15: 0000000000000000 > Object at ffff880160ef3600, in cache kmalloc-128 size: 128 > Allocated: > PID = 1730 > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 > save_stack+0x43/0xd0 mm/kasan/kasan.c:502 > set_track mm/kasan/kasan.c:514 [inline] > kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605 > kmem_cache_alloc_trace+0x10b/0x670 mm/slab.c:3634 > kmalloc include/linux/slab.h:490 [inline] > ida_pre_get+0xcd/0xe0 lib/radix-tree.c:2129 > proc_alloc_inum+0xc5/0x1f0 fs/proc/generic.c:197 > proc_register+0x25/0x2f0 fs/proc/generic.c:338 > proc_create_data+0x100/0x190 fs/proc/generic.c:509 > proc_create include/linux/proc_fs.h:35 [inline] > packet_net_init+0x8d/0xb0 net/packet/af_packet.c:4488 > ops_init+0x10a/0x530 net/core/net_namespace.c:115 > setup_net+0x2ed/0x690 net/core/net_namespace.c:291 > copy_net_ns+0x26c/0x530 net/core/net_namespace.c:396 > create_new_namespaces+0x409/0x860 kernel/nsproxy.c:106 > unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205 > SYSC_unshare kernel/fork.c:2281 [inline] > SyS_unshare+0x64e/0xfc0 kernel/fork.c:2231 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > Freed: > PID = 1648 > save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 > save_stack+0x43/0xd0 mm/kasan/kasan.c:502 > set_track mm/kasan/kasan.c:514 [inline] > kasan_slab_free+0x6f/0xb0 mm/kasan/kasan.c:578 > __cache_free mm/slab.c:3510 [inline] > kfree+0xd3/0x250 mm/slab.c:3827 > ida_pre_get+0x8a/0xe0 lib/radix-tree.c:2133 > ida_simple_get+0x168/0x320 lib/idr.c:443 > __kernfs_new_node+0xfe/0x3c0 fs/kernfs/dir.c:633 > kernfs_new_node+0x80/0xe0 fs/kernfs/dir.c:661 > kernfs_create_dir_ns+0x41/0x140 fs/kernfs/dir.c:933 > kernfs_create_dir include/linux/kernfs.h:477 [inline] > internal_create_group+0xf7/0x8f0 fs/sysfs/group.c:124 > sysfs_create_group fs/sysfs/group.c:156 [inline] > sysfs_create_groups+0x97/0x130 fs/sysfs/group.c:183 > device_add_groups drivers/base/core.c:1031 [inline] > device_add_attrs drivers/base/core.c:1058 [inline] > device_add+0xb2f/0x1650 drivers/base/core.c:1679 > netdev_register_kobject+0x183/0x360 net/core/net-sysfs.c:1603 > register_netdevice+0xa27/0xed0 net/core/dev.c:7228 > tun_set_iff drivers/net/tun.c:1843 [inline] > __tun_chr_ioctl+0x1bd0/0x3b70 drivers/net/tun.c:2046 > tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2291 > vfs_ioctl fs/ioctl.c:43 [inline] > do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:683 > SYSC_ioctl fs/ioctl.c:698 [inline] > SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689 > entry_SYSCALL_64_fastpath+0x1f/0xc2 > Memory state around the buggy address: > ffff880160ef3500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb > ffff880160ef3580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >>ffff880160ef3600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff880160ef3680: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00 > ffff880160ef3700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc > ================================================================== > > > I think we need: > > diff --git a/lib/radix-tree.c b/lib/radix-tree.c > index 5ed506d648c4..d435916f6527 100644 > --- a/lib/radix-tree.c > +++ b/lib/radix-tree.c > @@ -2129,8 +2129,8 @@ int ida_pre_get(struct ida *ida, gfp_t gfp) > struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp); > if (!bitmap) > return 0; > - bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap); > - kfree(bitmap); > + if (!this_cpu_cmpxchg(ida_bitmap, NULL, bitmap)) > + kfree(bitmap);
I meant: + if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap)) + kfree(bitmap); > } > > > Otherwise we both free the still installed old pointer and leak the new one.
