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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-03-11 00:25:26 -0500
committerPablo Neira Ayuso <pablo@netfilter.org>2017-03-13 13:33:58 +0100
commit170a1fb9c01bc40b7e8fd57a32ac9a0e131ec5b6 (patch)
treefee6768d3251ba6df0f65a3a5ae10e1c4ed05871 /net
parent4ca60d08cbe65f501baad64af50fceba79c19fbb (diff)
netfilter: Force fake conntrack entry to be at least 8 bytes aligned
Since the nfct and nfctinfo have been combined, the nf_conn structure must be at least 8 bytes aligned, as the 3 LSB bits are used for the nfctinfo. But there's a fake nf_conn structure to denote untracked connections, which is created by a PER_CPU construct. This does not guarantee that it will be 8 bytes aligned and can break the logic in determining the correct nfctinfo. I triggered this on a 32bit machine with the following error: BUG: unable to handle kernel NULL pointer dereference at 00000af4 IP: nf_ct_deliver_cached_events+0x1b/0xfb *pdpt = 0000000031962001 *pde = 0000000000000000 Oops: 0000 [#1] SMP [Modules linked in: ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables ipv6 crc_ccitt ppdev r8169 parport_pc parport OK ] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.0-test+ #75 Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014 task: c126ec00 task.stack: c1258000 EIP: nf_ct_deliver_cached_events+0x1b/0xfb EFLAGS: 00010202 CPU: 0 EAX: 0021cd01 EBX: 00000000 ECX: 27b0c767 EDX: 32bcb17a ESI: f34135c0 EDI: f34135c0 EBP: f2debd60 ESP: f2debd3c DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 CR0: 80050033 CR2: 00000af4 CR3: 309a0440 CR4: 001406f0 Call Trace: <SOFTIRQ> ? ipv6_skip_exthdr+0xac/0xcb ipv6_confirm+0x10c/0x119 [nf_conntrack_ipv6] nf_hook_slow+0x22/0xc7 nf_hook+0x9a/0xad [ipv6] ? ip6t_do_table+0x356/0x379 [ip6_tables] ? ip6_fragment+0x9e9/0x9e9 [ipv6] ip6_output+0xee/0x107 [ipv6] ? ip6_fragment+0x9e9/0x9e9 [ipv6] dst_output+0x36/0x4d [ipv6] NF_HOOK.constprop.37+0xb2/0xba [ipv6] ? icmp6_dst_alloc+0x2c/0xfd [ipv6] ? local_bh_enable+0x14/0x14 [ipv6] mld_sendpack+0x1c5/0x281 [ipv6] ? mark_held_locks+0x40/0x5c mld_ifc_timer_expire+0x1f6/0x21e [ipv6] call_timer_fn+0x135/0x283 ? detach_if_pending+0x55/0x55 ? mld_dad_timer_expire+0x3e/0x3e [ipv6] __run_timers+0x111/0x14b ? mld_dad_timer_expire+0x3e/0x3e [ipv6] run_timer_softirq+0x1c/0x36 __do_softirq+0x185/0x37c ? test_ti_thread_flag.constprop.19+0xd/0xd do_softirq_own_stack+0x22/0x28 </SOFTIRQ> irq_exit+0x5a/0xa4 smp_apic_timer_interrupt+0x2a/0x34 apic_timer_interrupt+0x37/0x3c By using DEFINE/DECLARE_PER_CPU_ALIGNED we can enforce at least 8 byte alignment as all cache line sizes are at least 8 bytes or more. Fixes: a9e419dc7be6 ("netfilter: merge ctinfo into nfct pointer storage area") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nf_conntrack_core.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 071b97fcbefb..ffb78e5f7b70 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -181,7 +181,11 @@ EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);
unsigned int nf_conntrack_max __read_mostly;
seqcount_t nf_conntrack_generation __read_mostly;
-DEFINE_PER_CPU(struct nf_conn, nf_conntrack_untracked);
+/* nf_conn must be 8 bytes aligned, as the 3 LSB bits are used
+ * for the nfctinfo. We cheat by (ab)using the PER CPU cache line
+ * alignment to enforce this.
+ */
+DEFINE_PER_CPU_ALIGNED(struct nf_conn, nf_conntrack_untracked);
EXPORT_PER_CPU_SYMBOL(nf_conntrack_untracked);
static unsigned int nf_conntrack_hash_rnd __read_mostly;