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Subject[PATCH 4.9 60/71] inet: frags: fix ip6frag_low_thresh boundary
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Dumazet <edumazet@google.com>

Giving an integer to proc_doulongvec_minmax() is dangerous on 64bit arches,
since linker might place next to it a non zero value preventing a change
to ip6frag_low_thresh.

ip6frag_low_thresh is not used anymore in the kernel, but we do not
want to prematuraly break user scripts wanting to change it.

Since specifying a minimal value of 0 for proc_doulongvec_minmax()
is moot, let's remove these zero values in all defrag units.

Fixes: 6e00f7dd5e4e ("ipv6: frags: fix /proc/sys/net/ipv6/ip6frag_low_thresh")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 3d23401283e80ceb03f765842787e0e79ff598b7)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ieee802154/6lowpan/reassembly.c | 2 -
net/ipv4/ip_fragment.c | 40 ++++++++++++--------------------
net/ipv6/netfilter/nf_conntrack_reasm.c | 2 -
net/ipv6/reassembly.c | 4 ---
4 files changed, 17 insertions(+), 31 deletions(-)

--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -410,7 +410,6 @@ err:
}

#ifdef CONFIG_SYSCTL
-static long zero;

static struct ctl_table lowpan_frags_ns_ctl_table[] = {
{
@@ -427,7 +426,6 @@ static struct ctl_table lowpan_frags_ns_
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
- .extra1 = &zero,
.extra2 = &init_net.ieee802154_lowpan.frags.high_thresh
},
{
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -56,14 +56,6 @@
*/
static const char ip_frag_cache_name[] = "ip4-frags";

-struct ipfrag_skb_cb
-{
- struct inet_skb_parm h;
- int offset;
-};
-
-#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
-
/* Describe an entry in the "incomplete datagrams" queue. */
struct ipq {
struct inet_frag_queue q;
@@ -351,13 +343,13 @@ static int ip_frag_queue(struct ipq *qp,
* this fragment, right?
*/
prev = qp->q.fragments_tail;
- if (!prev || FRAG_CB(prev)->offset < offset) {
+ if (!prev || prev->ip_defrag_offset < offset) {
next = NULL;
goto found;
}
prev = NULL;
for (next = qp->q.fragments; next != NULL; next = next->next) {
- if (FRAG_CB(next)->offset >= offset)
+ if (next->ip_defrag_offset >= offset)
break; /* bingo! */
prev = next;
}
@@ -368,7 +360,7 @@ found:
* any overlaps are eliminated.
*/
if (prev) {
- int i = (FRAG_CB(prev)->offset + prev->len) - offset;
+ int i = (prev->ip_defrag_offset + prev->len) - offset;

if (i > 0) {
offset += i;
@@ -385,8 +377,8 @@ found:

err = -ENOMEM;

- while (next && FRAG_CB(next)->offset < end) {
- int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
+ while (next && next->ip_defrag_offset < end) {
+ int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */

if (i < next->len) {
int delta = -next->truesize;
@@ -399,7 +391,7 @@ found:
delta += next->truesize;
if (delta)
add_frag_mem_limit(qp->q.net, delta);
- FRAG_CB(next)->offset += i;
+ next->ip_defrag_offset += i;
qp->q.meat -= i;
if (next->ip_summed != CHECKSUM_UNNECESSARY)
next->ip_summed = CHECKSUM_NONE;
@@ -423,7 +415,13 @@ found:
}
}

- FRAG_CB(skb)->offset = offset;
+ /* Note : skb->ip_defrag_offset and skb->dev share the same location */
+ dev = skb->dev;
+ if (dev)
+ qp->iif = dev->ifindex;
+ /* Makes sure compiler wont do silly aliasing games */
+ barrier();
+ skb->ip_defrag_offset = offset;

/* Insert this fragment in the chain of fragments. */
skb->next = next;
@@ -434,11 +432,6 @@ found:
else
qp->q.fragments = skb;

- dev = skb->dev;
- if (dev) {
- qp->iif = dev->ifindex;
- skb->dev = NULL;
- }
qp->q.stamp = skb->tstamp;
qp->q.meat += skb->len;
qp->ecn |= ecn;
@@ -514,7 +507,7 @@ static int ip_frag_reasm(struct ipq *qp,
}

WARN_ON(!head);
- WARN_ON(FRAG_CB(head)->offset != 0);
+ WARN_ON(head->ip_defrag_offset != 0);

/* Allocate a new buffer for the datagram. */
ihlen = ip_hdrlen(head);
@@ -677,7 +670,7 @@ struct sk_buff *ip_check_defrag(struct n
EXPORT_SYMBOL(ip_check_defrag);

#ifdef CONFIG_SYSCTL
-static long zero;
+static int dist_min;

static struct ctl_table ip4_frags_ns_ctl_table[] = {
{
@@ -694,7 +687,6 @@ static struct ctl_table ip4_frags_ns_ctl
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
- .extra1 = &zero,
.extra2 = &init_net.ipv4.frags.high_thresh
},
{
@@ -710,7 +702,7 @@ static struct ctl_table ip4_frags_ns_ctl
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
- .extra1 = &zero
+ .extra1 = &dist_min,
},
{ }
};
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -63,7 +63,6 @@ struct nf_ct_frag6_skb_cb
static struct inet_frags nf_frags;

#ifdef CONFIG_SYSCTL
-static long zero;

static struct ctl_table nf_ct_frag6_sysctl_table[] = {
{
@@ -79,7 +78,6 @@ static struct ctl_table nf_ct_frag6_sysc
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
- .extra1 = &zero,
.extra2 = &init_net.nf_frag.frags.high_thresh
},
{
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -548,7 +548,6 @@ static const struct inet6_protocol frag_
};

#ifdef CONFIG_SYSCTL
-static int zero;

static struct ctl_table ip6_frags_ns_ctl_table[] = {
{
@@ -564,8 +563,7 @@ static struct ctl_table ip6_frags_ns_ctl
.data = &init_net.ipv6.frags.low_thresh,
.maxlen = sizeof(unsigned long),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = &zero,
+ .proc_handler = proc_doulongvec_minmax,
.extra2 = &init_net.ipv6.frags.high_thresh
},
{

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