From 6b73d19711d0989cbdcd19c61faa0f79a1a5e466 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 27 May 2019 16:56:47 -0700 Subject: [PATCH 1/3] inet: frags: uninline fqdir_init() fqdir_init() is not fast path and is getting bigger. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inet_frag.h | 20 +------------------- net/ipv4/inet_fragment.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+), 19 deletions(-) diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 002f23c1a1a7..94092b1ef22e 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -109,25 +109,7 @@ struct inet_frags { int inet_frags_init(struct inet_frags *); void inet_frags_fini(struct inet_frags *); -static inline int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, - struct net *net) -{ - struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL); - int res; - - if (!fqdir) - return -ENOMEM; - fqdir->f = f; - fqdir->net = net; - res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params); - if (res < 0) { - kfree(fqdir); - return res; - } - *fqdirp = fqdir; - return 0; -} - +int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net); void fqdir_exit(struct fqdir *fqdir); void inet_frag_kill(struct inet_frag_queue *q); diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 6ca9523374da..7c07aae969e6 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -154,6 +154,25 @@ static void fqdir_rwork_fn(struct work_struct *work) kfree(fqdir); } +int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net) +{ + struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL); + int res; + + if (!fqdir) + return -ENOMEM; + fqdir->f = f; + fqdir->net = net; + res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params); + if (res < 0) { + kfree(fqdir); + return res; + } + *fqdirp = fqdir; + return 0; +} +EXPORT_SYMBOL(fqdir_init); + void fqdir_exit(struct fqdir *fqdir) { fqdir->high_thresh = 0; /* prevent creation of new frags */ From ae7352d384a552d8c799c242e74a934809990a71 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 27 May 2019 16:56:48 -0700 Subject: [PATCH 2/3] inet: frags: call inet_frags_fini() after unregister_pernet_subsys() Both IPv6 and 6lowpan are calling inet_frags_fini() too soon. inet_frags_fini() is dismantling a kmem_cache, that might be needed later when unregister_pernet_subsys() eventually has to remove frags queues from hash tables and free them. This fixes potential use-after-free, and is a prereq for the following patch. Fixes: d4ad4d22e7ac ("inet: frags: use kmem_cache for inet_frag_queue") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ieee802154/6lowpan/reassembly.c | 2 +- net/ipv6/reassembly.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c index e59c3b708969..5b56f16ed86b 100644 --- a/net/ieee802154/6lowpan/reassembly.c +++ b/net/ieee802154/6lowpan/reassembly.c @@ -540,7 +540,7 @@ err_sysctl: void lowpan_net_frag_exit(void) { - inet_frags_fini(&lowpan_frags); lowpan_frags_sysctl_unregister(); unregister_pernet_subsys(&lowpan_frags_ops); + inet_frags_fini(&lowpan_frags); } diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c index 836ea964cf14..ff5b6d8de2c6 100644 --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -583,8 +583,8 @@ err_protocol: void ipv6_frag_exit(void) { - inet_frags_fini(&ip6_frags); ip6_frags_sysctl_unregister(); unregister_pernet_subsys(&ip6_frags_ops); inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT); + inet_frags_fini(&ip6_frags); } From dc93f46bc4e00899eaf4579962cfac8cf2f9966d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 27 May 2019 16:56:49 -0700 Subject: [PATCH 3/3] 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: __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 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 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 Reported-by: syzbot Signed-off-by: David S. Miller --- include/net/inet_frag.h | 3 +++ net/ipv4/inet_fragment.c | 20 ++++++++++++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 94092b1ef22e..e91b79ad4e4a 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -3,6 +3,7 @@ #define __NET_FRAG_H__ #include +#include /* Per netns frag queues directory */ struct fqdir { @@ -104,6 +105,8 @@ struct inet_frags { struct kmem_cache *frags_cachep; const char *frags_cache_name; struct rhashtable_params rhash_params; + refcount_t refcnt; + struct completion completion; }; int inet_frags_init(struct inet_frags *); diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 7c07aae969e6..2b816f1ebbb4 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -110,14 +110,18 @@ int inet_frags_init(struct inet_frags *f) if (!f->frags_cachep) return -ENOMEM; + refcount_set(&f->refcnt, 1); + init_completion(&f->completion); return 0; } EXPORT_SYMBOL(inet_frags_init); void inet_frags_fini(struct inet_frags *f) { - /* We must wait that all inet_frag_destroy_rcu() have completed. */ - rcu_barrier(); + if (refcount_dec_and_test(&f->refcnt)) + complete(&f->completion); + + wait_for_completion(&f->completion); kmem_cache_destroy(f->frags_cachep); f->frags_cachep = NULL; @@ -149,8 +153,19 @@ static void fqdir_rwork_fn(struct work_struct *work) { struct fqdir *fqdir = container_of(to_rcu_work(work), struct fqdir, destroy_rwork); + struct inet_frags *f = fqdir->f; rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL); + + /* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu) + * have completed, since they need to dereference fqdir. + * Would it not be nice to have kfree_rcu_barrier() ? :) + */ + rcu_barrier(); + + if (refcount_dec_and_test(&f->refcnt)) + complete(&f->completion); + kfree(fqdir); } @@ -168,6 +183,7 @@ int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net) kfree(fqdir); return res; } + refcount_inc(&f->refcnt); *fqdirp = fqdir; return 0; }