Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_ct: fix skb leak and crash on ooo frags

act_ct adds skb->users before defragmentation. If frags arrive in order, the last frag's reference is reset in:

inet_frag_reasm_prepare skb_morph

which is not straightforward.

However when frags arrive out of order, nobody unref the last frag, and all frags are leaked. The situation is even worse, as initiating packet capture can lead to a crash[0] when skb has been cloned and shared at the same time.

Fix the issue by removing skb_get() before defragmentation. act_ct returns TC_ACT_CONSUMED when defrag failed or in progress.

[0]: [ 843.804823] ------------[ cut here ]------------ [ 843.809659] kernel BUG at net/core/skbuff.c:2091! [ 843.814516] invalid opcode: 0000 [#1] PREEMPT SMP [ 843.819296] CPU: 7 PID: 0 Comm: swapper/7 Kdump: loaded Tainted: G S 6.7.0-rc3 #2 [ 843.824107] Hardware name: XFUSION 1288H V6/BC13MBSBD, BIOS 1.29 11/25/2022 [ 843.828953] RIP: 0010:pskb_expand_head+0x2ac/0x300 [ 843.833805] Code: 8b 70 28 48 85 f6 74 82 48 83 c6 08 bf 01 00 00 00 e8 38 bd ff ff 8b 83 c0 00 00 00 48 03 83 c8 00 00 00 e9 62 ff ff ff 0f 0b <0f> 0b e8 8d d0 ff ff e9 b3 fd ff ff 81 7c 24 14 40 01 00 00 4c 89 [ 843.843698] RSP: 0018:ffffc9000cce07c0 EFLAGS: 00010202 [ 843.848524] RAX: 0000000000000002 RBX: ffff88811a211d00 RCX: 0000000000000820 [ 843.853299] RDX: 0000000000000640 RSI: 0000000000000000 RDI: ffff88811a211d00 [ 843.857974]…