This is a note to let you know that I've just added the patch titled
net: sched: fix memory leak in tcindex_set_parms
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-sched-fix-memory-leak-in-tcindex_set_parms.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1ec8a17054a30fe7fe0405e46c24de60de5b1cc1
Author: Hawkins Jiawei <yin31149@xxxxxxxxx>
Date: Thu Dec 22 11:51:19 2022 +0800
net: sched: fix memory leak in tcindex_set_parms
[ 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@xxxxxxxxxx/
Reported-by: syzbot+232ebdbd36706c965ebf@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+232ebdbd36706c965ebf@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);
