Commits
Eric Dumazet committed dc93f46bc4e
inet: frags: fix use-after-free read in inet_frag_destroy_rcu
As caught by syzbot [1], the rcu grace period that is respected
before fqdir_rwork_fn() proceeds and frees fqdir is not enough
to prevent inet_frag_destroy_rcu() being run after the freeing.
We need a proper rcu_barrier() synchronization to replace
the one we had in inet_frags_fini()
We also have to fix a potential problem at module removal :
inet_frags_fini() needs to make sure that all queued work queues
(fqdir_rwork_fn) have completed, otherwise we might
call kmem_cache_destroy() too soon and get another use-after-free.
[1]
BUG: KASAN: use-after-free in inet_frag_destroy_rcu+0xd9/0xe0 net/ipv4/inet_fragment.c:201
Read of size 8 at addr ffff88806ed47a18 by task swapper/1/0
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.2.0-rc1+ #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
__kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
kasan_report+0x12/0x20 mm/kasan/common.c:614
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
inet_frag_destroy_rcu+0xd9/0xe0 net/ipv4/inet_fragment.c:201
__rcu_reclaim kernel/rcu/rcu.h:222 [inline]
rcu_do_batch kernel/rcu/tree.c:2092 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2310 [inline]
rcu_core+0xba5/0x1500 kernel/rcu/tree.c:2291
__do_softirq+0x25c/0x94c kernel/softirq.c:293
invoke_softirq kernel/softirq.c:374 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:414
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x13b/0x550 arch/x86/kernel/apic/apic.c:1068
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:806
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: ff ff 48 89 df e8 f2 95 8c fa eb 82 e9 07 00 00 00 0f 00 2d e4 45 4b 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d d4 45 4b 00 fb f4 <c3> 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 e8 8e 18 42 fa e8 99
RSP: 0018:ffff8880a98e7d78 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1164e11 RBX: ffff8880a98d4340 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffff8880a98d4bbc
RBP: ffff8880a98e7da8 R08: ffff8880a98d4340 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffffffff88b27078 R14: 0000000000000001 R15: 0000000000000000
arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571
default_idle_call+0x36/0x90 kernel/sched/idle.c:94
cpuidle_idle_call kernel/sched/idle.c:154 [inline]
do_idle+0x377/0x560 kernel/sched/idle.c:263
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:354
start_secondary+0x34e/0x4c0 arch/x86/kernel/smpboot.c:267
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
Allocated by task 8877:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_kmalloc mm/kasan/common.c:489 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503
kmem_cache_alloc_trace+0x151/0x750 mm/slab.c:3555
kmalloc include/linux/slab.h:547 [inline]
kzalloc include/linux/slab.h:742 [inline]
fqdir_init include/net/inet_frag.h:115 [inline]
ipv6_frags_init_net+0x48/0x460 net/ipv6/reassembly.c:513
ops_init+0xb3/0x410 net/core/net_namespace.c:130
setup_net+0x2d3/0x740 net/core/net_namespace.c:316
copy_net_ns+0x1df/0x340 net/core/net_namespace.c:439
create_new_namespaces+0x400/0x7b0 kernel/nsproxy.c:107
unshare_nsproxy_namespaces+0xc2/0x200 kernel/nsproxy.c:206
ksys_unshare+0x440/0x980 kernel/fork.c:2692
__do_sys_unshare kernel/fork.c:2760 [inline]
__se_sys_unshare kernel/fork.c:2758 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:2758
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 17:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
__cache_free mm/slab.c:3432 [inline]
kfree+0xcf/0x220 mm/slab.c:3755
fqdir_rwork_fn+0x33/0x40 net/ipv4/inet_fragment.c:154
process_one_work+0x989/0x1790 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x354/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
The buggy address belongs to the object at ffff88806ed47a00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
512-byte region [ffff88806ed47a00, ffff88806ed47c00)
The buggy address belongs to the page:
page:ffffea0001bb51c0 refcount:1 mapcount:0 mapping:ffff8880aa400940 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000282a788 ffffea0001bb53c8 ffff8880aa400940
raw: 0000000000000000 ffff88806ed47000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff88806ed47900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806ed47980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88806ed47a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806ed47a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806ed47b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: 3c8fc8782044 ("inet: frags: rework rhashtable dismantle")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>