CVE-2021-47250

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

net: ipv4: fix memory leak in netlbl_cipsov4_add_std

Reported by syzkaller: BUG: memory leak unreferenced object 0xffff888105df7000 (size 64): comm syz-executor842, pid 360, jiffies 4294824824 (age 22.546s) hex dump (first 32 bytes): 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 00 00 00 00 00 00 ……………. backtrace: [<00000000e67ed558>] kmalloc include/linux/slab.h:590 [inline] [<00000000e67ed558>] kzalloc include/linux/slab.h:720 [inline] [<00000000e67ed558>] netlbl_cipsov4_add_std net/netlabel/netlabel_cipso_v4.c:145 [inline] [<00000000e67ed558>] netlbl_cipsov4_add+0x390/0x2340 net/netlabel/netlabel_cipso_v4.c:416 [<0000000006040154>] genl_family_rcv_msg_doit.isra.0+0x20e/0x320 net/netlink/genetlink.c:739 [<00000000204d7a1c>] genl_family_rcv_msg net/netlink/genetlink.c:783 [inline] [<00000000204d7a1c>] genl_rcv_msg+0x2bf/0x4f0 net/netlink/genetlink.c:800 [<00000000c0d6a995>] netlink_rcv_skb+0x134/0x3d0 net/netlink/af_netlink.c:2504 [<00000000d78b9d2c>] genl_rcv+0x24/0x40 net/netlink/genetlink.c:811 [<000000009733081b>] netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] [<000000009733081b>] netlink_unicast+0x4a0/0x6a0 net/netlink/af_netlink.c:1340 [<00000000d5fd43b8>] netlink_sendmsg+0x789/0xc70 net/netlink/af_netlink.c:1929 [<000000000a2d1e40>] sock_sendmsg_nosec net/socket.c:654 [inline] [<000000000a2d1e40>] sock_sendmsg+0x139/0x170 net/socket.c:674 [<00000000321d1969>] ____sys_sendmsg+0x658/0x7d0 net/socket.c:2350 [<00000000964e16bc>] ___sys_sendmsg+0xf8/0x170 net/socket.c:2404 [<000000001615e288>] __sys_sendmsg+0xd3/0x190 net/socket.c:2433 [<000000004ee8b6a5>] do_syscall_64+0x37/0x90 arch/x86/entry/common.c:47 [<00000000171c7cee>] entry_SYSCALL_64_after_hwframe+0x44/0xae

The memory of doi_def->map.std pointing is allocated in netlbl_cipsov4_add_std, but no place has freed it. It should be freed in cipso_v4_doi_free which frees the cipso DOI resource.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

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/086e92b1d68c6338535f715aad173f8cf4bfbc8c
• https://git.kernel.org/stable/c/0ffb460be3abac86f884a8c548bb02724ec370f4
• https://git.kernel.org/stable/c/212166510582631994be4f4b3fe15e10a03c1dd4
• https://git.kernel.org/stable/c/398a24447eb60f060c8994221cb5ae6caf355fa1
• https://git.kernel.org/stable/c/5340858147e3dc60913fb3dd0cbb758ec4a26e66
• https://git.kernel.org/stable/c/6dcea66d3bb519b426282588f38e884e07893c1f
• https://git.kernel.org/stable/c/d612c3f3fae221e7ea736d196581c2217304bbbc
• https://git.kernel.org/stable/c/deeeb65c6ee404f2d1fb80b38b2730645c0f4663
• https://git.kernel.org/stable/c/086e92b1d68c6338535f715aad173f8cf4bfbc8c
• https://git.kernel.org/stable/c/0ffb460be3abac86f884a8c548bb02724ec370f4
• https://git.kernel.org/stable/c/212166510582631994be4f4b3fe15e10a03c1dd4
• https://git.kernel.org/stable/c/398a24447eb60f060c8994221cb5ae6caf355fa1
• https://git.kernel.org/stable/c/5340858147e3dc60913fb3dd0cbb758ec4a26e66
• https://git.kernel.org/stable/c/6dcea66d3bb519b426282588f38e884e07893c1f
• https://git.kernel.org/stable/c/d612c3f3fae221e7ea736d196581c2217304bbbc
• https://git.kernel.org/stable/c/deeeb65c6ee404f2d1fb80b38b2730645c0f4663