From: Eric Dumazet edumazet@google.com
commit 2baae3545327632167c0180e9ca1d467416f1919 upstream.
synchronize_rcu() is fine when the rcu callbacks only need to free memory (kfree_rcu() or direct kfree() call rcu call backs)
__dev_map_entry_free() is a bit more complex, so we need to make sure that call queued __dev_map_entry_free() callbacks have completed.
sysbot report:
BUG: KASAN: use-after-free in dev_map_flush_old kernel/bpf/devmap.c:365 [inline] BUG: KASAN: use-after-free in __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 Read of size 8 at addr ffff8801b8da38c8 by task ksoftirqd/1/18
CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 4.17.0+ #39 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+0x1b9/0x294 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 dev_map_flush_old kernel/bpf/devmap.c:365 [inline] __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 __rcu_reclaim kernel/rcu/rcu.h:178 [inline] rcu_do_batch kernel/rcu/tree.c:2558 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2818 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2785 [inline] rcu_process_callbacks+0xe9d/0x1760 kernel/rcu/tree.c:2802 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:284 run_ksoftirqd+0x86/0x100 kernel/softirq.c:645 smpboot_thread_fn+0x417/0x870 kernel/smpboot.c:164 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Allocated by task 6675: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620 kmalloc include/linux/slab.h:513 [inline] kzalloc include/linux/slab.h:706 [inline] dev_map_alloc+0x208/0x7f0 kernel/bpf/devmap.c:102 find_and_alloc_map kernel/bpf/syscall.c:129 [inline] map_create+0x393/0x1010 kernel/bpf/syscall.c:453 __do_sys_bpf kernel/bpf/syscall.c:2351 [inline] __se_sys_bpf kernel/bpf/syscall.c:2328 [inline] __x64_sys_bpf+0x303/0x510 kernel/bpf/syscall.c:2328 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 26: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kfree+0xd9/0x260 mm/slab.c:3813 dev_map_free+0x4fa/0x670 kernel/bpf/devmap.c:191 bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:262 process_one_work+0xc64/0x1b70 kernel/workqueue.c:2153 worker_thread+0x181/0x13a0 kernel/workqueue.c:2296 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
The buggy address belongs to the object at ffff8801b8da37c0 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 264 bytes inside of 512-byte region [ffff8801b8da37c0, ffff8801b8da39c0) The buggy address belongs to the page: page:ffffea0006e368c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0xffff8801b8da3540 flags: 0x2fffc0000000100(slab) raw: 02fffc0000000100 ffffea0007217b88 ffffea0006e30cc8 ffff8801da800940 raw: ffff8801b8da3540 ffff8801b8da3040 0000000100000004 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff8801b8da3780: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff8801b8da3800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b8da3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff8801b8da3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b8da3980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
Fixes: 546ac1ffb70d ("bpf: add devmap, a map for storing net device references") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot+457d3e2ffbcf31aee5c0@syzkaller.appspotmail.com Acked-by: Toke Høiland-Jørgensen toke@redhat.com Acked-by: Jesper Dangaard Brouer brouer@redhat.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/bpf/devmap.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -164,6 +164,9 @@ static void dev_map_free(struct bpf_map bpf_clear_redirect_map(map); synchronize_rcu();
+ /* Make sure prior __dev_map_entry_free() have completed. */ + rcu_barrier(); + /* To ensure all pending flush operations have completed wait for flush * bitmap to indicate all flush_needed bits to be zero on _all_ cpus. * Because the above synchronize_rcu() ensures the map is disconnected