CVE-2022-49636

In the Linux kernel, the following vulnerability has been resolved:

vlan: fix memory leak in vlan_newlink()

Blamed commit added back a bug I fixed in commit 9bbd917e0bec (vlan: fix memory leak in vlan_dev_set_egress_priority)

If a memory allocation fails in vlan_changelink() after other allocations succeeded, we need to call vlan_dev_free_egress_priority() to free all allocated memory because after a failed ->newlink() we do not call any methods like ndo_uninit() or dev->priv_destructor().

In following example, if the allocation for last element 2000:2001 fails, we need to free eight prior allocations:

ip link add link dummy0 dummy0.100 type vlan id 100 egress-qos-map 1:2 2:3 3:4 4:5 5:6 6:7 7:8 8:9 2000:2001

syzbot report was:

BUG: memory leak unreferenced object 0xffff888117bd1060 (size 32): comm syz-executor408, pid 3759, jiffies 4294956555 (age 34.090s) hex dump (first 32 bytes): 09 00 00 00 00 a0 00 00 00 00 00 00 00 00 00 00 ……………. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. backtrace: [] kmalloc include/linux/slab.h:600 [inline] [] vlan_dev_set_egress_priority+0xed/0x170 net/8021q/vlan_dev.c:193 [] vlan_changelink+0x178/0x1d0 net/8021q/vlan_netlink.c:128 [] vlan_newlink+0x148/0x260 net/8021q/vlan_netlink.c:185 [] rtnl_newlink_create net/core/rtnetlink.c:3363 [inline] [] __rtnl_newlink+0xa58/0xdc0 net/core/rtnetlink.c:3580 [] rtnl_newlink+0x49/0x70 net/core/rtnetlink.c:3593 [] rtnetlink_rcv_msg+0x21c/0x5c0 net/core/rtnetlink.c:6089 [] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2501 [] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] [] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345 [] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921 [] sock_sendmsg_nosec net/socket.c:714 [inline] [] sock_sendmsg+0x56/0x80 net/socket.c:734 [] ____sys_sendmsg+0x36c/0x390 net/socket.c:2488 [] ___sys_sendmsg+0x8b/0xd0 net/socket.c:2542 [] __sys_sendmsg net/socket.c:2571 [inline] [] __do_sys_sendmsg net/socket.c:2580 [inline] [] __se_sys_sendmsg net/socket.c:2578 [inline] [] __x64_sys_sendmsg+0x78/0xf0 net/socket.c:2578 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [] entry_SYSCALL_64_after_hwframe+0x46/0xb0

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/4c43069bb1097dd6cc1cf0f7c43a36d1f7b3910b
• https://git.kernel.org/stable/c/72a0b329114b1caa8e69dfa7cdad1dd3c69b8602