CVE-2022-50396

In the Linux kernel, the following vulnerability has been resolved: net: sched: fix memory leak in tcindex_set_parms Syzkaller reports a memory leak as follows: ==================================== BUG: memory leak unreferenced object 0xffff88810c287f00 (size 256): comm "syz-executor105", pid 3600, jiffies 4294943292 (age 12.990s) 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: [ ] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046 [ ] kmalloc include/linux/slab.h:576 [inline] [ ] kmalloc_array include/linux/slab.h:627 [inline] [ ] kcalloc include/linux/slab.h:659 [inline] [ ] tcf_exts_init include/net/pkt_cls.h:250 [inline] [ ] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342 [ ] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553 [ ] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147 [ ] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082 [ ] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540 [ ] 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+0x178/0x410 net/socket.c:2482 [ ] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536 [ ] __sys_sendmmsg+0x105/0x330 net/socket.c:2622 [ ] __do_sys_sendmmsg net/socket.c:2651 [inline] [ ] __se_sys_sendmmsg net/socket.c:2648 [inline] [ ] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648 [ ] 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+0x63/0xcd ==================================== Kernel uses tcindex_change() to change an existing filter properties. Yet the problem is that, during the process of changing, if `old_r` is retrieved from `p->perfect`, then kernel uses tcindex_alloc_perfect_hash() to newly allocate filter results, uses tcindex_filter_result_init() to clear the old filter result, without destroying its tcf_exts structure, which triggers the above memory leak. To be more specific, there are only two source for the `old_r`, according to the tcindex_lookup(). `old_r` is retrieved from `p->perfect`, or `old_r` is retrieved from `p->h`. * If `old_r` is retrieved from `p->perfect`, kernel uses tcindex_alloc_perfect_hash() to newly allocate the filter results. Then `r` is assigned with `cp->perfect + handle`, which is newly allocated. So condition `old_r && old_r != r` is true in this situation, and kernel uses tcindex_filter_result_init() to clear the old filter result, without destroying its tcf_exts structure * If `old_r` is retrieved from `p->h`, then `p->perfect` is NULL according to the tcindex_lookup(). Considering that `cp->h` is directly copied from `p->h` and `p->perfect` is NULL, `r` is assigned with `tcindex_lookup(cp, handle)`, whose value should be the same as `old_r`, so condition `old_r && old_r != r` is false in this situation, kernel ignores using tcindex_filter_result_init() to clear the old filter result. So only when `old_r` is retrieved from `p->perfect` does kernel use tcindex_filter_result_init() to clear the old filter result, which triggers the above memory leak. Considering that there already exists a tc_filter_wq workqueue to destroy the old tcindex_d ---truncated---