[PATCH v5.15 0/2] Fix for CVE-2024-36901

[PATCH v5.15 0/2] Fix for CVE-2024-36901

[Ashwin Kamat]

From: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>

net/ipv6: annotate data-races around cnf.disable_ipv6 
       disable_ipv6 is read locklessly, add appropriate READ_ONCE() and WRITE_ONCE() annotations.

net/ipv6: prevent NULL dereference in ip6_output()
       Fix for CVE-2024-36901

Ashwin Dayanand Kamat (2):
       net/ipv6: annotate data-races around cnf.disable_ipv6
       net/ipv6: prevent NULL dereference in ip6_output()

 net/ipv6/addrconf.c   | 9 +++++----
 net/ipv6/ip6_input.c  | 2 +-
 net/ipv6/ip6_output.c | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

-- 
2.7.4

[PATCH v5.15 1/2] net/ipv6: annotate data-races around cnf.disable_ipv6

[Ashwin Kamat]

From: Eric Dumazet <edumazet@google.com>

[Upstream commit d289ab65b89c1d4d88417cb6c03e923f21f95fae]

disable_ipv6 is read locklessly, add appropriate READ_ONCE()
and WRITE_ONCE() annotations.

v2: do not preload net before rtnl_trylock() in
    addrconf_disable_ipv6() (Jiri)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 4db783d68b9b ("ipv6: prevent NULL dereference in ip6_output()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[Ashwin: Regenerated the Patch for v5.15]
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>
---
 net/ipv6/addrconf.c   | 9 +++++----
 net/ipv6/ip6_input.c  | 2 +-
 net/ipv6/ip6_output.c | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index a17e1d744b2d..ba22470b7476 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4131,7 +4131,7 @@ static void addrconf_dad_work(struct work_struct *w)
 			if (!ipv6_generate_eui64(addr.s6_addr + 8, idev->dev) &&
 			    ipv6_addr_equal(&ifp->addr, &addr)) {
 				/* DAD failed for link-local based on MAC */
-				idev->cnf.disable_ipv6 = 1;
+				WRITE_ONCE(idev->cnf.disable_ipv6, 1);
 
 				pr_info("%s: IPv6 being disabled!\n",
 					ifp->idev->dev->name);
@@ -6277,7 +6277,8 @@ static void addrconf_disable_change(struct net *net, __s32 newf)
 		idev = __in6_dev_get(dev);
 		if (idev) {
 			int changed = (!idev->cnf.disable_ipv6) ^ (!newf);
-			idev->cnf.disable_ipv6 = newf;
+
+			WRITE_ONCE(idev->cnf.disable_ipv6, newf);
 			if (changed)
 				dev_disable_change(idev);
 		}
@@ -6294,7 +6295,7 @@ static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int newf)
 
 	net = (struct net *)table->extra2;
 	old = *p;
-	*p = newf;
+	WRITE_ONCE(*p, newf);
 
 	if (p == &net->ipv6.devconf_dflt->disable_ipv6) {
 		rtnl_unlock();
@@ -6302,7 +6303,7 @@ static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int newf)
 	}
 
 	if (p == &net->ipv6.devconf_all->disable_ipv6) {
-		net->ipv6.devconf_dflt->disable_ipv6 = newf;
+		WRITE_ONCE(net->ipv6.devconf_dflt->disable_ipv6, newf);
 		addrconf_disable_change(net, newf);
 	} else if ((!newf) ^ (!old))
 		dev_disable_change((struct inet6_dev *)table->extra1);
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 32071529bfd9..c1c29432367c 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -164,7 +164,7 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 	__IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 
 	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
-	    !idev || unlikely(idev->cnf.disable_ipv6)) {
+	    !idev || unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 		goto drop;
 	}
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7205473ba28d..770ee7ffb0d5 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -221,7 +221,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	skb->protocol = htons(ETH_P_IPV6);
 	skb->dev = dev;
 
-	if (unlikely(idev->cnf.disable_ipv6)) {
+	if (unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
 		IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
 		kfree_skb(skb);
 		return 0;
-- 
2.45.1

[PATCH v5.15 2/2] net/ipv6: prevent NULL dereference in ip6_output()

[Ashwin Kamat]

From: Eric Dumazet <edumazet@google.com>

[Upstream commit 4db783d68b9b39a411a96096c10828ff5dfada7a]

According to syzbot, there is a chance that ip6_dst_idev()
returns NULL in ip6_output(). Most places in IPv6 stack
deal with a NULL idev just fine, but not here.

syzbot reported:

general protection fault, probably for non-canonical address 0xdffffc00000000bc: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000005e0-0x00000000000005e7]
CPU: 0 PID: 9775 Comm: syz-executor.4 Not tainted 6.9.0-rc5-syzkaller-00157-g6a30653b604a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
 RIP: 0010:ip6_output+0x231/0x3f0 net/ipv6/ip6_output.c:237
Code: 3c 1e 00 49 89 df 74 08 4c 89 ef e8 19 58 db f7 48 8b 44 24 20 49 89 45 00 49 89 c5 48 8d 9d e0 05 00 00 48 89 d8 48 c1 e8 03 <42> 0f b6 04 38 84 c0 4c 8b 74 24 28 0f 85 61 01 00 00 8b 1b 31 ff
RSP: 0018:ffffc9000927f0d8 EFLAGS: 00010202
RAX: 00000000000000bc RBX: 00000000000005e0 RCX: 0000000000040000
RDX: ffffc900131f9000 RSI: 0000000000004f47 RDI: 0000000000004f48
RBP: 0000000000000000 R08: ffffffff8a1f0b9a R09: 1ffffffff1f51fad
R10: dffffc0000000000 R11: fffffbfff1f51fae R12: ffff8880293ec8c0
R13: ffff88805d7fc000 R14: 1ffff1100527d91a R15: dffffc0000000000
FS:  00007f135c6856c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 0000000064096000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ip6_xmit+0xefe/0x17f0 net/ipv6/ip6_output.c:358
  sctp_v6_xmit+0x9f2/0x13f0 net/sctp/ipv6.c:248
  sctp_packet_transmit+0x26ad/0x2ca0 net/sctp/output.c:653
  sctp_packet_singleton+0x22c/0x320 net/sctp/outqueue.c:783
  sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
  sctp_outq_flush+0x6d5/0x3e20 net/sctp/outqueue.c:1212
  sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
  sctp_do_sm+0x59cc/0x60c0 net/sctp/sm_sideeffect.c:1169
  sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73
  __sctp_connect+0x9cd/0xe30 net/sctp/socket.c:1234
  sctp_connect net/sctp/socket.c:4819 [inline]
  sctp_inet_connect+0x149/0x1f0 net/sctp/socket.c:4834
  __sys_connect_file net/socket.c:2048 [inline]
  __sys_connect+0x2df/0x310 net/socket.c:2065
  __do_sys_connect net/socket.c:2075 [inline]
  __se_sys_connect net/socket.c:2072 [inline]
  __x64_sys_connect+0x7a/0x90 net/socket.c:2072
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: 778d80be5269 ("ipv6: Add disable_ipv6 sysctl to disable IPv6 operaion on specific interface.")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20240507161842.773961-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[Ashwin: Regenerated the Patch for v5.15]
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>
---
 net/ipv6/ip6_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 770ee7ffb0d5..ce37c8345579 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -221,7 +221,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	skb->protocol = htons(ETH_P_IPV6);
 	skb->dev = dev;
 
-	if (unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
+	if (unlikely(!idev || READ_ONCE(idev->cnf.disable_ipv6))) {
 		IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
 		kfree_skb(skb);
 		return 0;
-- 
2.45.1

Re: [PATCH v5.15 0/2] Fix for CVE-2024-36901

[Florian Fainelli]

[-- Attachment #1: Type: text/plain, Size: 688 bytes --]

On 7/9/24 03:19, Ashwin Kamat wrote:
> From: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>
> 
> net/ipv6: annotate data-races around cnf.disable_ipv6
>         disable_ipv6 is read locklessly, add appropriate READ_ONCE() and WRITE_ONCE() annotations.
> 
> net/ipv6: prevent NULL dereference in ip6_output()
>         Fix for CVE-2024-36901

LGTM!

> 
> Ashwin Dayanand Kamat (2):
>         net/ipv6: annotate data-races around cnf.disable_ipv6
>         net/ipv6: prevent NULL dereference in ip6_output()
> 
>   net/ipv6/addrconf.c   | 9 +++++----
>   net/ipv6/ip6_input.c  | 2 +-
>   net/ipv6/ip6_output.c | 2 +-
>   3 files changed, 7 insertions(+), 6 deletions(-)
> 

-- 
Florian


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