[PATCH 6.1 192/219] ipmr: fix kernel panic when forwarding mcast packets

Greg Kroah-Hartman
2024-02-03T04:10:55Z

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>

[ Upstream commit e622502c310f1069fd9f41cd38210553115f610a ]

The stacktrace was:
[ 86.305548] BUG: kernel NULL pointer dereference, address: 0000000000000092
[ 86.306815] #PF: supervisor read access in kernel mode
[ 86.307717] #PF: error_code(0x0000) - not-present page
[ 86.308624] PGD 0 P4D 0
[ 86.309091] Oops: 0000 [#1] PREEMPT SMP NOPTI
[ 86.309883] CPU: 2 PID: 3139 Comm: pimd Tainted: G U 6.8.0-6wind-knet #1
[ 86.311027] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.1-0-g0551a4be2c-prebuilt.qemu-project.org 04/01/2014
[ 86.312728] RIP: 0010:ip_mr_forward (/build/work/knet/net/ipv4/ipmr.c:1985)
[ 86.313399] Code: f9 1f 0f 87 85 03 00 00 48 8d 04 5b 48 8d 04 83 49 8d 44 c5 00 48 8b 40 70 48 39 c2 0f 84 d9 00 00 00 49 8b 46 58 48 83 e0 fe <80> b8 92 00 00 00 00 0f 84 55 ff ff ff 49 83 47 38 01 45 85 e4 0f
[ 86.316565] RSP: 0018:ffffad21c0583ae0 EFLAGS: 00010246
[ 86.317497] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 86.318596] RDX: ffff9559cb46c000 RSI: 0000000000000000 RDI: 0000000000000000
[ 86.319627] RBP: ffffad21c0583b30 R08: 0000000000000000 R09: 0000000000000000
[ 86.320650] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
[ 86.321672] R13: ffff9559c093a000 R14: ffff9559cc00b800 R15: ffff9559c09c1d80
[ 86.322873] FS: 00007f85db661980(0000) GS:ffff955a79d00000(0000) knlGS:0000000000000000
[ 86.324291] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 86.325314] CR2: 0000000000000092 CR3: 000000002f13a000 CR4: 0000000000350ef0
[ 86.326589] Call Trace:
[ 86.327036] <TASK>
[ 86.327434] ? show_regs (/build/work/knet/arch/x86/kernel/dumpstack.c:479)
[ 86.328049] ? __die (/build/work/knet/arch/x86/kernel/dumpstack.c:421 /build/work/knet/arch/x86/kernel/dumpstack.c:434)
[ 86.328508] ? page_fault_oops (/build/work/knet/arch/x86/mm/fault.c:707)
[ 86.329107] ? do_user_addr_fault (/build/work/knet/arch/x86/mm/fault.c:1264)
[ 86.329756] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.330350] ? __irq_work_queue_local (/build/work/knet/kernel/irq_work.c:111 (discriminator 1))
[ 86.331013] ? exc_page_fault (/build/work/knet/./arch/x86/include/asm/paravirt.h:693 /build/work/knet/arch/x86/mm/fault.c:1515 /build/work/knet/arch/x86/mm/fault.c:1563)
[ 86.331702] ? asm_exc_page_fault (/build/work/knet/./arch/x86/include/asm/idtentry.h:570)
[ 86.332468] ? ip_mr_forward (/build/work/knet/net/ipv4/ipmr.c:1985)
[ 86.333183] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.333920] ipmr_mfc_add (/build/work/knet/./include/linux/rcupdate.h:782 /build/work/knet/net/ipv4/ipmr.c:1009 /build/work/knet/net/ipv4/ipmr.c:1273)
[ 86.334583] ? __pfx_ipmr_hash_cmp (/build/work/knet/net/ipv4/ipmr.c:363)
[ 86.335357] ip_mroute_setsockopt (/build/work/knet/net/ipv4/ipmr.c:1470)
[ 86.336135] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.336854] ? ip_mroute_setsockopt (/build/work/knet/net/ipv4/ipmr.c:1470)
[ 86.337679] do_ip_setsockopt (/build/work/knet/net/ipv4/ip_sockglue.c:944)
[ 86.338408] ? __pfx_unix_stream_read_actor (/build/work/knet/net/unix/af_unix.c:2862)
[ 86.339232] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.339809] ? aa_sk_perm (/build/work/knet/security/apparmor/include/cred.h:153 /build/work/knet/security/apparmor/net.c:181)
[ 86.340342] ip_setsockopt (/build/work/knet/net/ipv4/ip_sockglue.c:1415)
[ 86.340859] raw_setsockopt (/build/work/knet/net/ipv4/raw.c:836)
[ 86.341408] ? security_socket_setsockopt (/build/work/knet/security/security.c:4561 (discriminator 13))
[ 86.342116] sock_common_setsockopt (/build/work/knet/net/core/sock.c:3716)
[ 86.342747] do_sock_setsockopt (/build/work/knet/net/socket.c:2313)
[ 86.343363] __sys_setsockopt (/build/work/knet/./include/linux/file.h:32 /build/work/knet/net/socket.c:2336)
[ 86.344020] __x64_sys_setsockopt (/build/work/knet/net/socket.c:2340)
[ 86.344766] do_syscall_64 (/build/work/knet/arch/x86/entry/common.c:52 /build/work/knet/arch/x86/entry/common.c:83)
[ 86.345433] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.346161] ? syscall_exit_work (/build/work/knet/./include/linux/audit.h:357 /build/work/knet/kernel/entry/common.c:160)
[ 86.346938] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.347657] ? syscall_exit_to_user_mode (/build/work/knet/kernel/entry/common.c:215)
[ 86.348538] ? srso_return_thunk (/build/work/knet/arch/x86/lib/retpoline.S:223)
[ 86.349262] ? do_syscall_64 (/build/work/knet/./arch/x86/include/asm/cpufeature.h:171 /build/work/knet/arch/x86/entry/common.c:98)
[ 86.349971] entry_SYSCALL_64_after_hwframe (/build/work/knet/arch/x86/entry/entry_64.S:129)

The original packet in ipmr_cache_report() may be queued and then forwarded
with ip_mr_forward(). This last function has the assumption that the skb
dst is set.

After the below commit, the skb dst is dropped by ipv4_pktinfo_prepare(),
which causes the oops.

Fixes: bb7403655b3c ("ipmr: support IP_PKTINFO on cache report IGMP msg")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240125141847.1931933-1-nicolas.dichtel@6wind.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/ip.h | 2 +-
net/ipv4/ip_sockglue.c | 6 ++++--
net/ipv4/ipmr.c | 2 +-
net/ipv4/raw.c | 2 +-
net/ipv4/udp.c | 2 +-
5 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index c83c09c65623..4f11f7df7dd6 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -752,7 +752,7 @@ int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev);
* Functions provided by ip_sockglue.c
*/

-void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb);
+void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb, bool drop_dst);
void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb, int tlen, int offset);
int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index c1fb7580ea58..a00ba2d51e1b 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1406,12 +1406,13 @@ int do_ip_setsockopt(struct sock *sk, int level, int optname,
* ipv4_pktinfo_prepare - transfer some info from rtable to skb
* @sk: socket
* @skb: buffer
+ * @drop_dst: if true, drops skb dst
*
* To support IP_CMSG_PKTINFO option, we store rt_iif and specific
* destination in skb->cb[] before dst drop.
* This way, receiver doesn't make cache line misses to read rtable.
*/
-void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb)
+void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb, bool drop_dst)
{
struct in_pktinfo *pktinfo = PKTINFO_SKB_CB(skb);
bool prepare = (inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO) ||
@@ -1440,7 +1441,8 @@ void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb)
pktinfo->ipi_ifindex = 0;
pktinfo->ipi_spec_dst.s_addr = 0;
}
- skb_dst_drop(skb);
+ if (drop_dst)
+ skb_dst_drop(skb);
}

int ip_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index b807197475a5..d5421c38c2aa 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1073,7 +1073,7 @@ static int ipmr_cache_report(const struct mr_table *mrt,
msg = (struct igmpmsg *)skb_network_header(skb);
msg->im_vif = vifi;
msg->im_vif_hi = vifi >> 8;
- ipv4_pktinfo_prepare(mroute_sk, pkt);
+ ipv4_pktinfo_prepare(mroute_sk, pkt, false);
memcpy(skb->cb, pkt->cb, sizeof(skb->cb));
/* Add our header */
igmp = skb_put(skb, sizeof(struct igmphdr));
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 19936dc329d8..7c63b91edbf7 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -290,7 +290,7 @@ static int raw_rcv_skb(struct sock *sk, struct sk_buff *skb)

/* Charge it to the socket. */

- ipv4_pktinfo_prepare(sk, skb);
+ ipv4_pktinfo_prepare(sk, skb, true);
if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0) {
kfree_skb_reason(skb, reason);
return NET_RX_DROP;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 11c0e1c66642..87d759bab001 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2196,7 +2196,7 @@ static int udp_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)

udp_csum_pull_header(skb);

- ipv4_pktinfo_prepare(sk, skb);
+ ipv4_pktinfo_prepare(sk, skb, true);
return __udp_queue_rcv_skb(sk, skb);

csum_error:
--
2.43.0