From 8675860592321a43bbb0b5aedc244a9b2321edc3 Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Tue, 18 Sep 2018 13:44:59 -0700 Subject: [PATCH 1/2] Revert "ipv6: fix double refcount of fib6_metrics" This reverts commit e70a3aad44cc8b24986687ffc98c4a4f6ecf25ea. This change causes use-after-free on dst->_metrics. The crash trace looks like this: [ 97.763269] BUG: KASAN: use-after-free in ip6_mtu+0x116/0x140 [ 97.769038] Read of size 4 at addr ffff881781d2cf84 by task svw_NetThreadEv/8801 [ 97.777954] CPU: 76 PID: 8801 Comm: svw_NetThreadEv Not tainted 4.15.0-smp-DEV #11 [ 97.777956] Hardware name: Default string Default string/Indus_QC_02, BIOS 5.46.4 03/29/2018 [ 97.777957] Call Trace: [ 97.777971] [] dump_stack+0x4d/0x72 [ 97.777985] [] print_address_description+0x6f/0x260 [ 97.777997] [] kasan_report+0x257/0x370 [ 97.778001] [] ? ip6_mtu+0x116/0x140 [ 97.778004] [] __asan_report_load4_noabort+0x19/0x20 [ 97.778008] [] ip6_mtu+0x116/0x140 [ 97.778013] [] tcp_current_mss+0x12e/0x280 [ 97.778016] [] ? tcp_mtu_to_mss+0x2d0/0x2d0 [ 97.778022] [] ? depot_save_stack+0x138/0x4a0 [ 97.778037] [] ? __mmdrop+0x145/0x1f0 [ 97.778040] [] ? save_stack+0xb1/0xd0 [ 97.778046] [] tcp_send_mss+0x22/0x220 [ 97.778059] [] tcp_sendmsg_locked+0x4f9/0x39f0 [ 97.778062] [] ? kasan_check_write+0x14/0x20 [ 97.778066] [] ? tcp_sendpage+0x60/0x60 [ 97.778070] [] ? rw_copy_check_uvector+0x69/0x280 [ 97.778075] [] ? import_iovec+0x9f/0x430 [ 97.778078] [] ? kasan_slab_free+0x87/0xc0 [ 97.778082] [] ? memzero_page+0x140/0x140 [ 97.778085] [] ? kasan_check_write+0x14/0x20 [ 97.778088] [] tcp_sendmsg+0x2c/0x50 [ 97.778092] [] ? tcp_sendmsg+0x2c/0x50 [ 97.778098] [] inet_sendmsg+0x103/0x480 [ 97.778102] [] ? inet_gso_segment+0x15b0/0x15b0 [ 97.778105] [] sock_sendmsg+0xba/0xf0 [ 97.778108] [] ___sys_sendmsg+0x6ca/0x8e0 [ 97.778113] [] ? hrtimer_try_to_cancel+0x71/0x3b0 [ 97.778116] [] ? copy_msghdr_from_user+0x3d0/0x3d0 [ 97.778119] [] ? memset+0x31/0x40 [ 97.778123] [] ? schedule_hrtimeout_range_clock+0x165/0x380 [ 97.778127] [] ? hrtimer_nanosleep_restart+0x250/0x250 [ 97.778130] [] ? __hrtimer_init+0x180/0x180 [ 97.778133] [] ? ktime_get_ts64+0x172/0x200 [ 97.778137] [] ? __fget_light+0x8c/0x2f0 [ 97.778141] [] __sys_sendmsg+0xe6/0x190 [ 97.778144] [] ? __sys_sendmsg+0xe6/0x190 [ 97.778147] [] ? SyS_shutdown+0x20/0x20 [ 97.778152] [] ? wake_up_q+0xe0/0xe0 [ 97.778155] [] ? __sys_sendmsg+0x190/0x190 [ 97.778158] [] SyS_sendmsg+0x13/0x20 [ 97.778162] [] do_syscall_64+0x2ac/0x430 [ 97.778166] [] ? do_page_fault+0x35/0x3d0 [ 97.778171] [] ? page_fault+0x2f/0x50 [ 97.778174] [] entry_SYSCALL_64_after_hwframe+0x3d/0xa2 [ 97.778177] RIP: 0033:0x7f83fa36000d [ 97.778178] RSP: 002b:00007f83ef9229e0 EFLAGS: 00000293 ORIG_RAX: 000000000000002e [ 97.778180] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f83fa36000d [ 97.778182] RDX: 0000000000004000 RSI: 00007f83ef922f00 RDI: 0000000000000036 [ 97.778183] RBP: 00007f83ef923040 R08: 00007f83ef9231f8 R09: 00007f83ef923168 [ 97.778184] R10: 0000000000000000 R11: 0000000000000293 R12: 00007f83f69c5b40 [ 97.778185] R13: 000000000000001c R14: 0000000000000001 R15: 0000000000004000 [ 97.779684] Allocated by task 5919: [ 97.783185] save_stack+0x46/0xd0 [ 97.783187] kasan_kmalloc+0xad/0xe0 [ 97.783189] kmem_cache_alloc_trace+0xdf/0x580 [ 97.783190] ip6_convert_metrics.isra.79+0x7e/0x190 [ 97.783192] ip6_route_info_create+0x60a/0x2480 [ 97.783193] ip6_route_add+0x1d/0x80 [ 97.783195] inet6_rtm_newroute+0xdd/0xf0 [ 97.783198] rtnetlink_rcv_msg+0x641/0xb10 [ 97.783200] netlink_rcv_skb+0x27b/0x3e0 [ 97.783202] rtnetlink_rcv+0x15/0x20 [ 97.783203] netlink_unicast+0x4be/0x720 [ 97.783204] netlink_sendmsg+0x7bc/0xbf0 [ 97.783205] sock_sendmsg+0xba/0xf0 [ 97.783207] ___sys_sendmsg+0x6ca/0x8e0 [ 97.783208] __sys_sendmsg+0xe6/0x190 [ 97.783209] SyS_sendmsg+0x13/0x20 [ 97.783211] do_syscall_64+0x2ac/0x430 [ 97.783213] entry_SYSCALL_64_after_hwframe+0x3d/0xa2 [ 97.784709] Freed by task 0: [ 97.785056] knetbase: Error: /proc/sys/net/core/txcs_enable does not exist [ 97.794497] save_stack+0x46/0xd0 [ 97.794499] kasan_slab_free+0x71/0xc0 [ 97.794500] kfree+0x7c/0xf0 [ 97.794501] fib6_info_destroy_rcu+0x24f/0x310 [ 97.794504] rcu_process_callbacks+0x38b/0x1730 [ 97.794506] __do_softirq+0x1c8/0x5d0 Reported-by: John Sperbeck Signed-off-by: Wei Wang Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Signed-off-by: David S. Miller --- net/ipv6/route.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 480a79f47c52..b5d3e6b294ab 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -976,6 +976,10 @@ static void rt6_set_from(struct rt6_info *rt, struct fib6_info *from) rt->rt6i_flags &= ~RTF_EXPIRES; rcu_assign_pointer(rt->from, from); dst_init_metrics(&rt->dst, from->fib6_metrics->metrics, true); + if (from->fib6_metrics != &dst_default_metrics) { + rt->dst._metrics |= DST_METRICS_REFCOUNTED; + refcount_inc(&from->fib6_metrics->refcnt); + } } /* Caller must already hold reference to @ort */ From ce7ea4af0838ffd4667ecad4eb5eec7a25342f1e Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Tue, 18 Sep 2018 13:45:00 -0700 Subject: [PATCH 2/2] ipv6: fix memory leak on dst->_metrics When dst->_metrics and f6i->fib6_metrics share the same memory, both take reference count on the dst_metrics structure. However, when dst is destroyed, ip6_dst_destroy() only invokes dst_destroy_metrics_generic() which does not take care of READONLY metrics and does not release refcnt. This causes memory leak. Similar to ipv4 logic, the fix is to properly release refcnt and free the memory space pointed by dst->_metrics if refcnt becomes 0. Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes") Reported-by: Sabrina Dubroca Signed-off-by: Wei Wang Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Signed-off-by: David S. Miller --- net/ipv6/route.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index b5d3e6b294ab..826b14de7dbb 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -364,11 +364,14 @@ EXPORT_SYMBOL(ip6_dst_alloc); static void ip6_dst_destroy(struct dst_entry *dst) { + struct dst_metrics *p = (struct dst_metrics *)DST_METRICS_PTR(dst); struct rt6_info *rt = (struct rt6_info *)dst; struct fib6_info *from; struct inet6_dev *idev; - dst_destroy_metrics_generic(dst); + if (p != &dst_default_metrics && refcount_dec_and_test(&p->refcnt)) + kfree(p); + rt6_uncached_list_del(rt); idev = rt->rt6i_idev;