On Wed, Sep 08, 2021 at 11:15:34AM +0100, Lee Jones wrote:

From: Liu Jian liujian56@huawei.com

[ Upstream commit 23d2b94043ca8835bd1e67749020e839f396a1c2 ]

I got below panic when doing fuzz test:

Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 4056 Comm: syz-executor.3 Tainted: G B 5.14.0-rc1-00195-gcff5c4254439-dirty #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack_lvl+0x7a/0x9b panic+0x2cd/0x5af end_report.cold+0x5a/0x5a kasan_report+0xec/0x110 ip_check_mc_rcu+0x556/0x5d0 __mkroute_output+0x895/0x1740 ip_route_output_key_hash_rcu+0x2d0/0x1050 ip_route_output_key_hash+0x182/0x2e0 ip_route_output_flow+0x28/0x130 udp_sendmsg+0x165d/0x2280 udpv6_sendmsg+0x121e/0x24f0 inet6_sendmsg+0xf7/0x140 sock_sendmsg+0xe9/0x180 ____sys_sendmsg+0x2b8/0x7a0 ___sys_sendmsg+0xf0/0x160 __sys_sendmmsg+0x17e/0x3c0 __x64_sys_sendmmsg+0x9e/0x100 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x462eb9 Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3df5af1c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462eb9 RDX: 0000000000000312 RSI: 0000000020001700 RDI: 0000000000000007 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3df5af26bc R13: 00000000004c372d R14: 0000000000700b10 R15: 00000000ffffffff

It is one use-after-free in ip_check_mc_rcu. In ip_mc_del_src, the ip_sf_list of pmc has been freed under pmc->lock protection. But access to ip_sf_list in ip_check_mc_rcu is not protected by the lock.

Cc: stable@vger.kernel.org # 4.4+ Signed-off-by: Liu Jian liujian56@huawei.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Lee Jones lee.jones@linaro.org

---

net/ipv4/igmp.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index 00576bae183d3..0c321996c6eb0 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -2720,6 +2720,7 @@ int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u rv = 1; } else if (im) { if (src_addr) {

• 	spin_lock_bh(&im->lock);
  for (psf = im->sources; psf; psf = psf->sf_next) {
  	if (psf->sf_inaddr == src_addr)
  		break;
  

@@ -2730,6 +2731,7 @@ int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u im->sfcount[MCAST_EXCLUDE]; else rv = im->sfcount[MCAST_EXCLUDE] != 0;

• 	spin_unlock_bh(&im->lock);
  

  } else rv = 1; /* unspecified source; tentatively allow */ }

-- 2.33.0.153.gba50c8fa24-goog

Now queued up, thanks.

greg k-h