This is a note to let you know that I've just added the patch titled
netlink: annotate lockless accesses to nlk->max_recvmsg_len
to the 6.1-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:
netlink-annotate-lockless-accesses-to-nlk-max_recvms.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6b1da1c18ca1fda19a3531dada852085d10ca1ba
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Mon Apr 3 21:46:43 2023 +0000
netlink: annotate lockless accesses to nlk->max_recvmsg_len
[ Upstream commit a1865f2e7d10dde00d35a2122b38d2e469ae67ed ]
syzbot reported a data-race in data-race in netlink_recvmsg() [1]
Indeed, netlink_recvmsg() can be run concurrently,
and netlink_dump() also needs protection.
[1]
BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg
read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0:
netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
__sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194
__do_sys_recvfrom net/socket.c:2212 [inline]
__se_sys_recvfrom net/socket.c:2208 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2208
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1:
netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989
sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
____sys_recvmsg+0x156/0x310 net/socket.c:2720
___sys_recvmsg net/socket.c:2762 [inline]
do_recvmmsg+0x2e5/0x710 net/socket.c:2856
__sys_recvmmsg net/socket.c:2935 [inline]
__do_sys_recvmmsg net/socket.c:2958 [inline]
__se_sys_recvmmsg net/socket.c:2951 [inline]
__x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x0000000000000000 -> 0x0000000000001000
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Fixes: 9063e21fb026 ("netlink: autosize skb lengthes")
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230403214643.768555-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index e506712967918..99622c64081c4 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1941,7 +1941,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
struct scm_cookie scm;
struct sock *sk = sock->sk;
struct netlink_sock *nlk = nlk_sk(sk);
- size_t copied;
+ size_t copied, max_recvmsg_len;
struct sk_buff *skb, *data_skb;
int err, ret;
@@ -1974,9 +1974,10 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
#endif
/* Record the max length of recvmsg() calls for future allocations */
- nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
- nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
- SKB_WITH_OVERHEAD(32768));
+ max_recvmsg_len = max(READ_ONCE(nlk->max_recvmsg_len), len);
+ max_recvmsg_len = min_t(size_t, max_recvmsg_len,
+ SKB_WITH_OVERHEAD(32768));
+ WRITE_ONCE(nlk->max_recvmsg_len, max_recvmsg_len);
copied = data_skb->len;
if (len < copied) {
@@ -2225,6 +2226,7 @@ static int netlink_dump(struct sock *sk)
struct netlink_ext_ack extack = {};
struct netlink_callback *cb;
struct sk_buff *skb = NULL;
+ size_t max_recvmsg_len;
struct module *module;
int err = -ENOBUFS;
int alloc_min_size;
@@ -2247,8 +2249,9 @@ static int netlink_dump(struct sock *sk)
cb = &nlk->cb;
alloc_min_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
- if (alloc_min_size < nlk->max_recvmsg_len) {
- alloc_size = nlk->max_recvmsg_len;
+ max_recvmsg_len = READ_ONCE(nlk->max_recvmsg_len);
+ if (alloc_min_size < max_recvmsg_len) {
+ alloc_size = max_recvmsg_len;
skb = alloc_skb(alloc_size,
(GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) |
__GFP_NOWARN | __GFP_NORETRY);
