From: Davide Caratti dcaratti@redhat.com
[ Upstream commit f77bd544a6bbe69aa50d9ed09f13494cf36ff806 ]
while testing re-assembly/re-fragmentation using act_ct, it's possible to observe a crash like the following one:
KASAN: maybe wild-memory-access in range [0x0001000000000448-0x000100000000044f] CPU: 50 PID: 0 Comm: swapper/50 Tainted: G S 5.12.0-rc7+ #424 Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.4.3 01/17/2017 RIP: 0010:inet_frag_rbtree_purge+0x50/0xc0 Code: 00 fc ff df 48 89 c3 31 ed 48 89 df e8 a9 7a 38 ff 4c 89 fe 48 89 df 49 89 c6 e8 5b 3a 38 ff 48 8d 7b 40 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00 75 59 48 8d bb d0 00 00 00 4c 8b 6b 40 48 89 f8 48 RSP: 0018:ffff888c31449db8 EFLAGS: 00010203 RAX: 0000200000000089 RBX: 000100000000040e RCX: ffffffff989eb960 RDX: 0000000000000140 RSI: ffffffff97cfb977 RDI: 000100000000044e RBP: 0000000000000900 R08: 0000000000000000 R09: ffffed1186289350 R10: 0000000000000003 R11: ffffed1186289350 R12: dffffc0000000000 R13: 000100000000040e R14: 0000000000000000 R15: ffff888155e02160 FS: 0000000000000000(0000) GS:ffff888c31440000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005600cb70a5b8 CR3: 0000000a2c014005 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> inet_frag_destroy+0xa9/0x150 call_timer_fn+0x2d/0x180 run_timer_softirq+0x4fe/0xe70 __do_softirq+0x197/0x5a0 irq_exit_rcu+0x1de/0x200 sysvec_apic_timer_interrupt+0x6b/0x80 </IRQ>
when act_ct temporarily stores an IP fragment, restoring the skb qdisc cb results in putting random data in FRAG_CB(), and this causes those "wild" memory accesses later, when the rbtree is purged. Never overwrite the skb cb in case tcf_ct_handle_fragments() returns -EINPROGRESS.
Fixes: ae372cb1750f ("net/sched: act_ct: fix restore the qdisc_skb_cb after defrag") Fixes: 7baf2429a1a9 ("net/sched: cls_flower add CT_FLAGS_INVALID flag support") Reported-by: Shuang Li shuali@redhat.com Signed-off-by: Davide Caratti dcaratti@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/act_ct.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c index 16e888a9601d..48fdf7293dea 100644 --- a/net/sched/act_ct.c +++ b/net/sched/act_ct.c @@ -732,7 +732,8 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb, #endif }
- *qdisc_skb_cb(skb) = cb; + if (err != -EINPROGRESS) + *qdisc_skb_cb(skb) = cb; skb_clear_hash(skb); skb->ignore_df = 1; return err; @@ -967,7 +968,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a, err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag); if (err == -EINPROGRESS) { retval = TC_ACT_STOLEN; - goto out; + goto out_clear; } if (err) goto drop; @@ -1030,7 +1031,6 @@ do_nat: out_push: skb_push_rcsum(skb, nh_ofs);
-out: qdisc_skb_cb(skb)->post_ct = true; out_clear: tcf_action_update_bstats(&c->common, skb);