From: Hawkins Jiawei yin31149@gmail.com
[ Upstream commit 399ab7fe0fa0d846881685fd4e57e9a8ef7559f7 ]
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: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()") Link: https://lore.kernel.org/all/0000000000001de5c505ebc9ec59@google.com/ Reported-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com Tested-by: syzbot+232ebdbd36706c965ebf@syzkaller.appspotmail.com Cc: Cong Wang cong.wang@bytedance.com Cc: Jakub Kicinski kuba@kernel.org Cc: Paolo Abeni pabeni@redhat.com Cc: Dmitry Vyukov dvyukov@google.com Acked-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Hawkins Jiawei yin31149@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/cls_tcindex.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c index 742c7d49a958..8d1ef858db87 100644 --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -332,7 +332,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, struct tcindex_filter_result *r, struct nlattr **tb, struct nlattr *est, u32 flags, struct netlink_ext_ack *extack) { - struct tcindex_filter_result new_filter_result, *old_r = r; + struct tcindex_filter_result new_filter_result; struct tcindex_data *cp = NULL, *oldp; struct tcindex_filter *f = NULL; /* make gcc behave */ struct tcf_result cr = {}; @@ -401,7 +401,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, err = tcindex_filter_result_init(&new_filter_result, cp, net); if (err < 0) goto errout_alloc; - if (old_r) + if (r) cr = r->res;
err = -EBUSY; @@ -478,14 +478,6 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, tcf_bind_filter(tp, &cr, base); }
- if (old_r && old_r != r) { - err = tcindex_filter_result_init(old_r, cp, net); - if (err < 0) { - kfree(f); - goto errout_alloc; - } - } - oldp = p; r->res = cr; tcf_exts_change(&r->exts, &e);