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authorDongseok Yi <dseok.yi@samsung.com>2021-01-08 11:28:38 +0900
committerJakub Kicinski <kuba@kernel.org>2021-01-08 19:14:02 -0800
commit53475c5dd856212e91538a9501162e821cc1f791 (patch)
treed3cb3b7fcd0ad741cb3bdb5d1706786b3582098a /net
parentafba9dc1f3a5390475006061c0bdc5ad4915878e (diff)
net: fix use-after-free when UDP GRO with shared fraglist
skbs in fraglist could be shared by a BPF filter loaded at TC. If TC writes, it will call skb_ensure_writable -> pskb_expand_head to create a private linear section for the head_skb. And then call skb_clone_fraglist -> skb_get on each skb in the fraglist. skb_segment_list overwrites part of the skb linear section of each fragment itself. Even after skb_clone, the frag_skbs share their linear section with their clone in PF_PACKET. Both sk_receive_queue of PF_PACKET and PF_INET (or PF_INET6) can have a link for the same frag_skbs chain. If a new skb (not frags) is queued to one of the sk_receive_queue, multiple ptypes can see and release this. It causes use-after-free. [ 4443.426215] ------------[ cut here ]------------ [ 4443.426222] refcount_t: underflow; use-after-free. [ 4443.426291] WARNING: CPU: 7 PID: 28161 at lib/refcount.c:190 refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426726] pstate: 60400005 (nZCv daif +PAN -UAO) [ 4443.426732] pc : refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426737] lr : refcount_dec_and_test_checked+0xa0/0xc8 [ 4443.426808] Call trace: [ 4443.426813] refcount_dec_and_test_checked+0xa4/0xc8 [ 4443.426823] skb_release_data+0x144/0x264 [ 4443.426828] kfree_skb+0x58/0xc4 [ 4443.426832] skb_queue_purge+0x64/0x9c [ 4443.426844] packet_set_ring+0x5f0/0x820 [ 4443.426849] packet_setsockopt+0x5a4/0xcd0 [ 4443.426853] __sys_setsockopt+0x188/0x278 [ 4443.426858] __arm64_sys_setsockopt+0x28/0x38 [ 4443.426869] el0_svc_common+0xf0/0x1d0 [ 4443.426873] el0_svc_handler+0x74/0x98 [ 4443.426880] el0_svc+0x8/0xc Fixes: 3a1296a38d0c (net: Support GRO/GSO fraglist chaining.) Signed-off-by: Dongseok Yi <dseok.yi@samsung.com> Acked-by: Willem de Bruijn <willemb@google.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/r/1610072918-174177-1-git-send-email-dseok.yi@samsung.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/core/skbuff.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f62cae3f75d8..b6f2b520a9b7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3655,7 +3655,8 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
unsigned int delta_truesize = 0;
unsigned int delta_len = 0;
struct sk_buff *tail = NULL;
- struct sk_buff *nskb;
+ struct sk_buff *nskb, *tmp;
+ int err;
skb_push(skb, -skb_network_offset(skb) + offset);
@@ -3665,11 +3666,28 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
nskb = list_skb;
list_skb = list_skb->next;
+ err = 0;
+ if (skb_shared(nskb)) {
+ tmp = skb_clone(nskb, GFP_ATOMIC);
+ if (tmp) {
+ consume_skb(nskb);
+ nskb = tmp;
+ err = skb_unclone(nskb, GFP_ATOMIC);
+ } else {
+ err = -ENOMEM;
+ }
+ }
+
if (!tail)
skb->next = nskb;
else
tail->next = nskb;
+ if (unlikely(err)) {
+ nskb->next = list_skb;
+ goto err_linearize;
+ }
+
tail = nskb;
delta_len += nskb->len;