CVE 2025 38248 cos

pocs/linux/kernelctf/CVE-2025-38248_cos/docs/vulnerability.md

@@ -1,5 +1,19 @@
-##bridge: mcast: Fix use-after-free during router port configuration
-[ Upstream commit 7544f3f5b0b58c396f374d060898b5939da31709 ]
+# Vulnerability Details
+
+- **Requirements**:
+    - **Capabilities**: `CAP_NET_ADMIN`
+    - **Kernel configuration**: `CONFIG_BRIDGE_IGMP_SNOOPING`
+    - **User namespaces required**: Yes
+- **Introduced by**:
+    - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4b30ae9adb04 ("net: bridge: mcast: re-implement br_multicast_{enable, disable}_port functions")
+    - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2796d846d74a ("net: bridge: vlan: convert mcast router global option to per-vlan entry")
+- **Fixed by**: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f05a4f9e959e0fc098046044c650acf897ea52d2
+- **Affected Versions**: `5.15 - 6.15.5`
+- **Affected Component**: `net/bridge` (multicast snooping)
+- **Cause**: Use-after-free
+- **Description**: When per-VLAN multicast snooping is toggled, `br_multicast_port_ctx_deinit()` only cancels multicast router timers but does not remove the port from the global (or per-VLAN) multicast router port lists. A port in permanent multicast router state (`mcast_router=2`) can be re-added to the router list after snooping mode changes, and when the port is subsequently deleted, a dangling pointer remains in the list. Traversing the list (e.g., when adding a new port) triggers a use-after-free on the freed `net_bridge_port` object.
+
+# Vulnerability Analysis
 
 The bridge maintains a global list of ports behind which a multicast
 router resides. The list is consulted during forwarding to ensure
@@ -10,21 +24,25 @@ When per-VLAN multicast snooping is enabled, the per-port multicast
 context is disabled on each port and the port is removed from the global
 router port list:
 
- # ip link add name br1 up type bridge vlan_filtering 1 mcast_snooping 1
- # ip link add name dummy1 up master br1 type dummy
- # ip link set dev dummy1 type bridge_slave mcast_router 2
- $ bridge -d mdb show | grep router
- router ports on br1: dummy1
- # ip link set dev br1 type bridge mcast_vlan_snooping 1
- $ bridge -d mdb show | grep router
+```bash
+# ip link add name br1 up type bridge vlan_filtering 1 mcast_snooping 1
+# ip link add name dummy1 up master br1 type dummy
+# ip link set dev dummy1 type bridge_slave mcast_router 2
+$ bridge -d mdb show | grep router
+router ports on br1: dummy1
+# ip link set dev br1 type bridge mcast_vlan_snooping 1
+$ bridge -d mdb show | grep router
+```
 
 However, the port can be re-added to the global list even when per-VLAN
 multicast snooping is enabled:
 
- # ip link set dev dummy1 type bridge_slave mcast_router 0
- # ip link set dev dummy1 type bridge_slave mcast_router 2
- $ bridge -d mdb show | grep router
- router ports on br1: dummy1
+```bash
+# ip link set dev dummy1 type bridge_slave mcast_router 0
+# ip link set dev dummy1 type bridge_slave mcast_router 2
+$ bridge -d mdb show | grep router
+router ports on br1: dummy1
+```
 
 Since commit 4b30ae9adb04 ("net: bridge: mcast: re-implement
 br_multicast_{enable, disable}_port functions"), when per-VLAN multicast
@@ -34,32 +52,38 @@ result, a port will remain in the global router port list even after it
 is deleted. This will lead to a use-after-free [1] when the list is
 traversed (when adding a new port to the list, for example):
 
- # ip link del dev dummy1
- # ip link add name dummy2 up master br1 type dummy
- # ip link set dev dummy2 type bridge_slave mcast_router 2
+```bash
+# ip link del dev dummy1
+# ip link add name dummy2 up master br1 type dummy
+# ip link set dev dummy2 type bridge_slave mcast_router 2
+```
 
 Similarly, stale entries can also be found in the per-VLAN router port
 list. When per-VLAN multicast snooping is disabled, the per-{port, VLAN}
 contexts are disabled on each port and the port is removed from the
 per-VLAN router port list:
 
- # ip link add name br1 up type bridge vlan_filtering 1 mcast_snooping 1 mcast_vlan_snooping 1
- # ip link add name dummy1 up master br1 type dummy
- # bridge vlan add vid 2 dev dummy1
- # bridge vlan global set vid 2 dev br1 mcast_snooping 1
- # bridge vlan set vid 2 dev dummy1 mcast_router 2
- $ bridge vlan global show dev br1 vid 2 | grep router
-       router ports: dummy1
- # ip link set dev br1 type bridge mcast_vlan_snooping 0
- $ bridge vlan global show dev br1 vid 2 | grep router
+```bash
+# ip link add name br1 up type bridge vlan_filtering 1 mcast_snooping 1 mcast_vlan_snooping 1
+# ip link add name dummy1 up master br1 type dummy
+# bridge vlan add vid 2 dev dummy1
+# bridge vlan global set vid 2 dev br1 mcast_snooping 1
+# bridge vlan set vid 2 dev dummy1 mcast_router 2
+$ bridge vlan global show dev br1 vid 2 | grep router
+      router ports: dummy1
+# ip link set dev br1 type bridge mcast_vlan_snooping 0
+$ bridge vlan global show dev br1 vid 2 | grep router
+```
 
 However, the port can be re-added to the per-VLAN list even when
 per-VLAN multicast snooping is disabled:
 
- # bridge vlan set vid 2 dev dummy1 mcast_router 0
- # bridge vlan set vid 2 dev dummy1 mcast_router 2
- $ bridge vlan global show dev br1 vid 2 | grep router
-       router ports: dummy1
+```bash
+# bridge vlan set vid 2 dev dummy1 mcast_router 0
+# bridge vlan set vid 2 dev dummy1 mcast_router 2
+$ bridge vlan global show dev br1 vid 2 | grep router
+      router ports: dummy1
+```
 
 When the VLAN is deleted from the port, the per-{port, VLAN} multicast
 context will not be disabled since multicast snooping is not enabled
@@ -68,80 +92,33 @@ port list even after it is no longer member in the VLAN. This will lead
 to a use-after-free [2] when the list is traversed (when adding a new
 port to the list, for example):
 
- # ip link add name dummy2 up master br1 type dummy
- # bridge vlan add vid 2 dev dummy2
- # bridge vlan del vid 2 dev dummy1
- # bridge vlan set vid 2 dev dummy2 mcast_router 2
-
-Fix these issues by removing the port from the relevant (global or
-per-VLAN) router port list in br_multicast_port_ctx_deinit(). The
-function is invoked during port deletion with the per-port multicast
-context and during VLAN deletion with the per-{port, VLAN} multicast
-context.
+```bash
+# ip link add name dummy2 up master br1 type dummy
+# bridge vlan add vid 2 dev dummy2
+# bridge vlan del vid 2 dev dummy1
+# bridge vlan set vid 2 dev dummy2 mcast_router 2
+```
+
+The root cause is that `br_multicast_port_ctx_deinit()` only cancels
+multicast router timers but does not remove the port from the router
+port lists:
+
+```c
+void br_multicast_port_ctx_deinit(struct net_bridge_mcast_port *pmctx)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+    del_timer_sync(&pmctx->ip6_mc_router_timer);
+#endif
+    del_timer_sync(&pmctx->ip4_mc_router_timer);
+    // Missing: br_ip4_multicast_rport_del(pmctx)
+    // Missing: br_ip6_multicast_rport_del(pmctx)
+}
+```
+
+The fix adds the missing list removal calls so that ports are properly
+unlinked from the router port lists during port/VLAN deletion.
 
 Note that deleting the multicast router timer is not enough as it only
 takes care of the temporary multicast router states (1 or 3) and not the
 permanent one (2).
 
-[1]
-BUG: KASAN: slab-out-of-bounds in br_multicast_add_router.part.0+0x3f1/0x560
-Write of size 8 at addr ffff888004a67328 by task ip/384
-[...]
-Call Trace:
- <TASK>
- dump_stack_lvl+0x6f/0xa0
- print_address_description.constprop.0+0x6f/0x350
- print_report+0x108/0x205
- kasan_report+0xdf/0x110
- br_multicast_add_router.part.0+0x3f1/0x560
- br_multicast_set_port_router+0x74e/0xac0
- br_setport+0xa55/0x1870
- br_port_slave_changelink+0x95/0x120
- __rtnl_newlink+0x5e8/0xa40
- rtnl_newlink+0x627/0xb00
- rtnetlink_rcv_msg+0x6fb/0xb70
- netlink_rcv_skb+0x11f/0x350
- netlink_unicast+0x426/0x710
- netlink_sendmsg+0x75a/0xc20
- __sock_sendmsg+0xc1/0x150
- ____sys_sendmsg+0x5aa/0x7b0
- ___sys_sendmsg+0xfc/0x180
- __sys_sendmsg+0x124/0x1c0
- do_syscall_64+0xbb/0x360
- entry_SYSCALL_64_after_hwframe+0x4b/0x53
-
-[2]
-BUG: KASAN: slab-use-after-free in br_multicast_add_router.part.0+0x378/0x560
-Read of size 8 at addr ffff888009f00840 by task bridge/391
-[...]
-Call Trace:
- <TASK>
- dump_stack_lvl+0x6f/0xa0
- print_address_description.constprop.0+0x6f/0x350
- print_report+0x108/0x205
- kasan_report+0xdf/0x110
- br_multicast_add_router.part.0+0x378/0x560
- br_multicast_set_port_router+0x6f9/0xac0
- br_vlan_process_options+0x8b6/0x1430
- br_vlan_rtm_process_one+0x605/0xa30
- br_vlan_rtm_process+0x396/0x4c0
- rtnetlink_rcv_msg+0x2f7/0xb70
- netlink_rcv_skb+0x11f/0x350
- netlink_unicast+0x426/0x710
- netlink_sendmsg+0x75a/0xc20
- __sock_sendmsg+0xc1/0x150
- ____sys_sendmsg+0x5aa/0x7b0
- ___sys_sendmsg+0xfc/0x180
- __sys_sendmsg+0x124/0x1c0
- do_syscall_64+0xbb/0x360
- entry_SYSCALL_64_after_hwframe+0x4b/0x53
-
-Fixes: 2796d846d74a ("net: bridge: vlan: convert mcast router global option to per-vlan entry")
-Fixes: 4b30ae9adb04 ("net: bridge: mcast: re-implement br_multicast_{enable, disable}_port functions")
-Reported-by: syzbot+7bfa4b72c6a5da128d32@syzkaller.appspotmail.com
-Closes: https://lore.kernel.org/all/684c18bd.a00a0220.279073.000b.GAE@google.com/T/
-Signed-off-by: Ido Schimmel <idosch@nvidia.com>
-Link: https://patch.msgid.link/20250619182228.1656906-1-idosch@nvidia.com
-Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-Signed-off-by: Sasha Levin <sashal@kernel.org>
-

pocs/linux/kernelctf/CVE-2025-38248_cos/exploit/cos-121-18867.294.25/Makefile

@@ -1,13 +1,20 @@
-CFLAGS = -static -pthread -s
+KERNELXDK_INCLUDE_DIR ?= /usr/local/include
+KERNELXDK_LIB_DIR ?= /usr/lib
 
+CXX = g++
+CXXFLAGS = -I. -I$(KERNELXDK_INCLUDE_DIR) -static -pthread -s
+LDFLAGS = -L$(KERNELXDK_LIB_DIR) -lkernelXDK -lkeyutils
 
-exploit: exploit.c
-	$(CC) $(CFLAGS) -o $@ $<
+exploit: exploit.cpp target_db.kxdb
+	$(CXX) $(CXXFLAGS) -o $@ $< $(LDFLAGS)
 
-exploit_debug: exploit.c
-	$(CC) $(CFLAGS) -o $@ $< -g
+exploit_debug: exploit.cpp target_db.kxdb
+	$(CXX) $(CXXFLAGS) -g -o $@ $< $(LDFLAGS)
+
+target_db.kxdb:
+	wget -O target_db.kxdb https://storage.googleapis.com/kernelxdk/db/kernelctf.kxdb
 
 clean:
-	rm -f exploit
+	rm -f exploit exploit_debug target_db.kxdb
 
 .PHONY: clean