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399ab7fe0f
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:
[<ffffffff814cf9f0>] kmalloc_trace+0x20/0x90 mm/slab_common.c:1046
[<ffffffff839c9e07>] kmalloc include/linux/slab.h:576 [inline]
[<ffffffff839c9e07>] kmalloc_array include/linux/slab.h:627 [inline]
[<ffffffff839c9e07>] kcalloc include/linux/slab.h:659 [inline]
[<ffffffff839c9e07>] tcf_exts_init include/net/pkt_cls.h:250 [inline]
[<ffffffff839c9e07>] tcindex_set_parms+0xa7/0xbe0 net/sched/cls_tcindex.c:342
[<ffffffff839caa1f>] tcindex_change+0xdf/0x120 net/sched/cls_tcindex.c:553
[<ffffffff8394db62>] tc_new_tfilter+0x4f2/0x1100 net/sched/cls_api.c:2147
[<ffffffff8389e91c>] rtnetlink_rcv_msg+0x4dc/0x5d0 net/core/rtnetlink.c:6082
[<ffffffff839eba67>] netlink_rcv_skb+0x87/0x1d0 net/netlink/af_netlink.c:2540
[<ffffffff839eab87>] netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
[<ffffffff839eab87>] netlink_unicast+0x397/0x4c0 net/netlink/af_netlink.c:1345
[<ffffffff839eb046>] netlink_sendmsg+0x396/0x710 net/netlink/af_netlink.c:1921
[<ffffffff8383e796>] sock_sendmsg_nosec net/socket.c:714 [inline]
[<ffffffff8383e796>] sock_sendmsg+0x56/0x80 net/socket.c:734
[<ffffffff8383eb08>] ____sys_sendmsg+0x178/0x410 net/socket.c:2482
[<ffffffff83843678>] ___sys_sendmsg+0xa8/0x110 net/socket.c:2536
[<ffffffff838439c5>] __sys_sendmmsg+0x105/0x330 net/socket.c:2622
[<ffffffff83843c14>] __do_sys_sendmmsg net/socket.c:2651 [inline]
[<ffffffff83843c14>] __se_sys_sendmmsg net/socket.c:2648 [inline]
[<ffffffff83843c14>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2648
[<ffffffff84605fd5>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84605fd5>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
[<ffffffff84800087>] 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_data by tcindex_partial_destroy_work()
at the end of tcindex_set_parms(), this patch solves
this memory leak bug by removing this old filter result
clearing part and delegating it to the tc_filter_wq workqueue.
Note that this patch doesn't introduce any other issues. If
`old_r` is retrieved from `p->perfect`, this patch just
delegates old filter result clearing part to the
tc_filter_wq workqueue; If `old_r` is retrieved from `p->h`,
kernel doesn't reach the old filter result clearing part, so
removing this part has no effect.
[Thanks to the suggestion from Jakub Kicinski, Cong Wang, Paolo Abeni
and Dmitry Vyukov]
Fixes:
|
||
|---|---|---|
| .. | ||
| 6lowpan | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| appletalk | ||
| atm | ||
| ax25 | ||
| batman-adv | ||
| bluetooth | ||
| bpf | ||
| bpfilter | ||
| bridge | ||
| caif | ||
| can | ||
| ceph | ||
| core | ||
| dcb | ||
| dccp | ||
| dns_resolver | ||
| dsa | ||
| ethernet | ||
| ethtool | ||
| hsr | ||
| ieee802154 | ||
| ife | ||
| ipv4 | ||
| ipv6 | ||
| iucv | ||
| kcm | ||
| key | ||
| l2tp | ||
| l3mdev | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| mac802154 | ||
| mctp | ||
| mpls | ||
| mptcp | ||
| ncsi | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| netrom | ||
| nfc | ||
| nsh | ||
| openvswitch | ||
| packet | ||
| phonet | ||
| psample | ||
| qrtr | ||
| rds | ||
| rfkill | ||
| rose | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| smc | ||
| strparser | ||
| sunrpc | ||
| switchdev | ||
| tipc | ||
| tls | ||
| unix | ||
| vmw_vsock | ||
| wireless | ||
| x25 | ||
| xdp | ||
| xfrm | ||
| compat.c | ||
| devres.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| socket.c | ||
| sysctl_net.c | ||