From: Vasily Averin vvs@virtuozzo.com

mainline inclusion from mainline-v5.15 commit 7f678def99d29c520418607509bb19c7fc96a6db category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9HVTH CVE: CVE-2024-26921

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

--------------------------------

Christoph Paasch reports [1] about incorrect skb->truesize after skb_expand_head() call in ip6_xmit. This may happen because of two reasons: - skb_set_owner_w() for newly cloned skb is called too early, before pskb_expand_head() where truesize is adjusted for (!skb-sk) case. - pskb_expand_head() does not adjust truesize in (skb->sk) case. In this case sk->sk_wmem_alloc should be adjusted too.

[1] https://lkml.org/lkml/2021/8/20/1082

Fixes: f1260ff15a71 ("skbuff: introduce skb_expand_head()") Fixes: 2d85a1b31dde ("ipv6: ip6_finish_output2: set sk into newly allocated nskb") Reported-by: Christoph Paasch christoph.paasch@gmail.com Signed-off-by: Vasily Averin vvs@virtuozzo.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/644330dd-477e-0462-83bf-9f514c41edd1@virtuozzo.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Ziyang Xuan william.xuanziyang@huawei.com --- net/core/skbuff.c | 36 +++++++++++++++++++++++------------- net/core/sock_destructor.h | 12 ++++++++++++ 2 files changed, 35 insertions(+), 13 deletions(-) create mode 100644 net/core/sock_destructor.h

diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 34f1a059afcd..6ac8c6f3a744 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -79,6 +79,7 @@ #include <linux/indirect_call_wrapper.h>

#include "datagram.h" +#include "sock_destructor.h"

struct kmem_cache *skbuff_head_cache __ro_after_init; static struct kmem_cache *skbuff_fclone_cache __ro_after_init; @@ -1788,30 +1789,39 @@ int __skb_unclone_keeptruesize(struct sk_buff *skb, gfp_t pri) struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom) { int delta = headroom - skb_headroom(skb); + int osize = skb_end_offset(skb); + struct sock *sk = skb->sk;

if (WARN_ONCE(delta <= 0, "%s is expecting an increase in the headroom", __func__)) return skb;

- /* pskb_expand_head() might crash, if skb is shared */ - if (skb_shared(skb)) { + delta = SKB_DATA_ALIGN(delta); + /* pskb_expand_head() might crash, if skb is shared. */ + if (skb_shared(skb) || !is_skb_wmem(skb)) { struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);

- if (likely(nskb)) { - if (skb->sk) - skb_set_owner_w(nskb, skb->sk); - consume_skb(skb); - } else { - kfree_skb(skb); - } + if (unlikely(!nskb)) + goto fail; + + if (sk) + skb_set_owner_w(nskb, sk); + consume_skb(skb); skb = nskb; } - if (skb && - pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { - kfree_skb(skb); - skb = NULL; + if (pskb_expand_head(skb, delta, 0, GFP_ATOMIC)) + goto fail; + + if (sk && is_skb_wmem(skb)) { + delta = skb_end_offset(skb) - osize; + refcount_add(delta, &sk->sk_wmem_alloc); + skb->truesize += delta; } return skb; + +fail: + kfree_skb(skb); + return NULL; } EXPORT_SYMBOL(skb_expand_head);

diff --git a/net/core/sock_destructor.h b/net/core/sock_destructor.h new file mode 100644 index 000000000000..2f396e6bfba5 --- /dev/null +++ b/net/core/sock_destructor.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _NET_CORE_SOCK_DESTRUCTOR_H +#define _NET_CORE_SOCK_DESTRUCTOR_H +#include <net/tcp.h> + +static inline bool is_skb_wmem(const struct sk_buff *skb) +{ + return skb->destructor == sock_wfree || + skb->destructor == __sock_wfree || + (IS_ENABLED(CONFIG_INET) && skb->destructor == tcp_wfree); +} +#endif

From: Florian Westphal fw@strlen.de

mainline inclusion from mainline-v6.9-rc2 commit 18685451fc4e546fc0e718580d32df3c0e5c8272 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9HVTH CVE: CVE-2024-26921

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

--------------------------------

ip_local_out() and other functions can pass skb->sk as function argument.

If the skb is a fragment and reassembly happens before such function call returns, the sk must not be released.

This affects skb fragments reassembled via netfilter or similar modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline.

Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing.

A relevant old patch about the issue was : 8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()")

[..]

net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one.

If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly.

We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used.

Eric suggested to stash sk in fragment queue and made an initial patch. However there is a problem with this:

If skb is refragmented again right after, ip_do_fragment() will copy head->sk to the new fragments, and sets up destructor to sock_wfree. IOW, we have no choice but to fix up sk_wmem accouting to reflect the fully reassembled skb, else wmem will underflow.

This change moves the orphan down into the core, to last possible moment. As ip_defrag_offset is aliased with sk_buff->sk member, we must move the offset into the FRAG_CB, else skb->sk gets clobbered.

This allows to delay the orphaning long enough to learn if the skb has to be queued or if the skb is completing the reasm queue.

In the former case, things work as before, skb is orphaned. This is safe because skb gets queued/stolen and won't continue past reasm engine.

In the latter case, we will steal the skb->sk reference, reattach it to the head skb, and fix up wmem accouting when inet_frag inflates truesize.

Fixes: 7026b1ddb6b8 ("netfilter: Pass socket pointer down through okfn().") Diagnosed-by: Eric Dumazet edumazet@google.com Reported-by: xingwei lee xrivendell7@gmail.com Reported-by: yue sun samsun1006219@gmail.com Reported-by: syzbot+e5167d7144a62715044c@syzkaller.appspotmail.com Signed-off-by: Florian Westphal fw@strlen.de Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/20240326101845.30836-1-fw@strlen.de Signed-off-by: Paolo Abeni pabeni@redhat.com Conflicts: net/ipv4/inet_fragment.c Signed-off-by: Ziyang Xuan william.xuanziyang@huawei.com --- include/linux/skbuff.h | 7 +-- net/ipv4/inet_fragment.c | 70 ++++++++++++++++++++----- net/ipv4/ip_fragment.c | 2 +- net/ipv6/netfilter/nf_conntrack_reasm.c | 2 +- 4 files changed, 60 insertions(+), 21 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index c3c89b6cc42f..a2f7293ba012 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -622,8 +622,6 @@ typedef unsigned char *sk_buff_data_t; * @rbnode: RB tree node, alternative to next/prev for netem/tcp * @list: queue head * @sk: Socket we are owned by - * @ip_defrag_offset: (aka @sk) alternate use of @sk, used in - * fragmentation management * @dev: Device we arrived on/are leaving by * @dev_scratch: (aka @dev) alternate use of @dev when @dev would be %NULL * @cb: Control buffer. Free for use by every layer. Put private vars here @@ -739,10 +737,7 @@ struct sk_buff { struct llist_node ll_node; };

- union { - struct sock *sk; - int ip_defrag_offset; - }; + struct sock *sk;

union { ktime_t tstamp; diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index e0e8a65d561e..9f315f74df4a 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -24,6 +24,8 @@ #include <net/ip.h> #include <net/ipv6.h>

+#include <net/tcp_ext.h> + /* Use skb->cb to track consecutive/adjacent fragments coming at * the end of the queue. Nodes in the rb-tree queue will * contain "runs" of one or more adjacent fragments. @@ -39,6 +41,7 @@ struct ipfrag_skb_cb { }; struct sk_buff *next_frag; int frag_run_len; + int ip_defrag_offset; };

#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb)) @@ -359,12 +362,12 @@ int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, */ if (!last) fragrun_create(q, skb); /* First fragment. */ - else if (last->ip_defrag_offset + last->len < end) { + else if (FRAG_CB(last)->ip_defrag_offset + last->len < end) { /* This is the common case: skb goes to the end. */ /* Detect and discard overlaps. */ - if (offset < last->ip_defrag_offset + last->len) + if (offset < FRAG_CB(last)->ip_defrag_offset + last->len) return IPFRAG_OVERLAP; - if (offset == last->ip_defrag_offset + last->len) + if (offset == FRAG_CB(last)->ip_defrag_offset + last->len) fragrun_append_to_last(q, skb); else fragrun_create(q, skb); @@ -381,13 +384,13 @@ int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,

parent = *rbn; curr = rb_to_skb(parent); - curr_run_end = curr->ip_defrag_offset + + curr_run_end = FRAG_CB(curr)->ip_defrag_offset + FRAG_CB(curr)->frag_run_len; - if (end <= curr->ip_defrag_offset) + if (end <= FRAG_CB(curr)->ip_defrag_offset) rbn = &parent->rb_left; else if (offset >= curr_run_end) rbn = &parent->rb_right; - else if (offset >= curr->ip_defrag_offset && + else if (offset >= FRAG_CB(curr)->ip_defrag_offset && end <= curr_run_end) return IPFRAG_DUP; else @@ -401,7 +404,7 @@ int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, rb_insert_color(&skb->rbnode, &q->rb_fragments); }

- skb->ip_defrag_offset = offset; + FRAG_CB(skb)->ip_defrag_offset = offset;

return IPFRAG_OK; } @@ -411,13 +414,28 @@ void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, struct sk_buff *parent) { struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments); - struct sk_buff **nextp; + void (*destructor)(struct sk_buff *); + unsigned int orig_truesize = 0; + struct sk_buff **nextp = NULL; + struct sock *sk = skb->sk; int delta;

+ if (sk && is_skb_wmem(skb)) { + /* TX: skb->sk might have been passed as argument to + * dst->output and must remain valid until tx completes. + * + * Move sk to reassembled skb and fix up wmem accounting. + */ + orig_truesize = skb->truesize; + destructor = skb->destructor; + } + if (head != skb) { fp = skb_clone(skb, GFP_ATOMIC); - if (!fp) - return NULL; + if (!fp) { + head = skb; + goto out_restore_sk; + } FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag; if (RB_EMPTY_NODE(&skb->rbnode)) FRAG_CB(parent)->next_frag = fp; @@ -426,6 +444,12 @@ void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, &q->rb_fragments); if (q->fragments_tail == skb) q->fragments_tail = fp; + + if (orig_truesize) { + /* prevent skb_morph from releasing sk */ + skb->sk = NULL; + skb->destructor = NULL; + } skb_morph(skb, head); FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag; rb_replace_node(&head->rbnode, &skb->rbnode, @@ -433,13 +457,13 @@ void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, consume_skb(head); head = skb; } - WARN_ON(head->ip_defrag_offset != 0); + WARN_ON(FRAG_CB(head)->ip_defrag_offset != 0);

delta = -head->truesize;

/* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) - return NULL; + goto out_restore_sk;

delta += head->truesize; if (delta) @@ -455,7 +479,7 @@ void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,

clone = alloc_skb(0, GFP_ATOMIC); if (!clone) - return NULL; + goto out_restore_sk; skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; skb_frag_list_init(head); for (i = 0; i < skb_shinfo(head)->nr_frags; i++) @@ -472,6 +496,21 @@ void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, nextp = &skb_shinfo(head)->frag_list; }

+out_restore_sk: + if (orig_truesize) { + int ts_delta = head->truesize - orig_truesize; + + /* if this reassembled skb is fragmented later, + * fraglist skbs will get skb->sk assigned from head->sk, + * and each frag skb will be released via sock_wfree. + * + * Update sk_wmem_alloc. + */ + head->sk = sk; + head->destructor = destructor; + refcount_add(ts_delta, &sk->sk_wmem_alloc); + } + return nextp; } EXPORT_SYMBOL(inet_frag_reasm_prepare); @@ -479,6 +518,8 @@ EXPORT_SYMBOL(inet_frag_reasm_prepare); void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head, void *reasm_data, bool try_coalesce) { + struct sock *sk = is_skb_wmem(head) ? head->sk : NULL; + const unsigned int head_truesize = head->truesize; struct sk_buff **nextp = (struct sk_buff **)reasm_data; struct rb_node *rbn; struct sk_buff *fp; @@ -541,6 +582,9 @@ void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head, skb_mark_not_on_list(head); head->prev = NULL; head->tstamp = q->stamp; + + if (sk) + refcount_add(sum_truesize - head_truesize, &sk->sk_wmem_alloc); } EXPORT_SYMBOL(inet_frag_reasm_finish);

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index fad803d2d711..ec2264adf2a6 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -377,6 +377,7 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) }

skb_dst_drop(skb); + skb_orphan(skb); return -EINPROGRESS;

insert_error: @@ -479,7 +480,6 @@ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user) struct ipq *qp;

__IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS); - skb_orphan(skb);

/* Lookup (or create) queue header */ qp = ip_find(net, ip_hdr(skb), user, vif); diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c index c129ad334eb3..8c2163f95711 100644 --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -296,6 +296,7 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb, }

skb_dst_drop(skb); + skb_orphan(skb); return -EINPROGRESS;

insert_error: @@ -471,7 +472,6 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user) hdr = ipv6_hdr(skb); fhdr = (struct frag_hdr *)skb_transport_header(skb);

- skb_orphan(skb); fq = fq_find(net, fhdr->identification, user, hdr, skb->dev ? skb->dev->ifindex : 0); if (fq == NULL) {