This is a note to let you know that I've just added the patch titled
kcm: fix 0-length case for kcm_sendmsg()
to the 4.9-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:
kcm-fix-0-length-case-for-kcm_sendmsg.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Feb 23 21:13:05 CET 2017
From: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Date: Tue, 7 Feb 2017 12:59:47 -0800
Subject: kcm: fix 0-length case for kcm_sendmsg()
From: WANG Cong <xiyou.wangcong@xxxxxxxxx>
[ Upstream commit 98e3862ca2b1ae595a13805dcab4c3a6d7718f4d ]
Dmitry reported a kernel warning:
WARNING: CPU: 3 PID: 2936 at net/kcm/kcmsock.c:627
kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
CPU: 3 PID: 2936 Comm: a.out Not tainted 4.10.0-rc6+ #209
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
panic+0x1fb/0x412 kernel/panic.c:179
__warn+0x1c4/0x1e0 kernel/panic.c:539
warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
kcm_write_msgs+0x12e3/0x1b90 net/kcm/kcmsock.c:627
kcm_sendmsg+0x163a/0x2200 net/kcm/kcmsock.c:1029
sock_sendmsg_nosec net/socket.c:635 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:645
sock_write_iter+0x326/0x600 net/socket.c:848
new_sync_write fs/read_write.c:499 [inline]
__vfs_write+0x483/0x740 fs/read_write.c:512
vfs_write+0x187/0x530 fs/read_write.c:560
SYSC_write fs/read_write.c:607 [inline]
SyS_write+0xfb/0x230 fs/read_write.c:599
entry_SYSCALL_64_fastpath+0x1f/0xc2
when calling syscall(__NR_write, sock2, 0x208aaf27ul, 0x0ul) on a KCM
seqpacket socket. It appears that kcm_sendmsg() does not handle len==0
case correctly, which causes an empty skb is allocated and queued.
Fix this by skipping the skb allocation for len==0 case.
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Tom Herbert <tom@xxxxxxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/kcm/kcmsock.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -929,23 +929,25 @@ static int kcm_sendmsg(struct socket *so
goto out_error;
}
- /* New message, alloc head skb */
- head = alloc_skb(0, sk->sk_allocation);
- while (!head) {
- kcm_push(kcm);
- err = sk_stream_wait_memory(sk, &timeo);
- if (err)
- goto out_error;
-
+ if (msg_data_left(msg)) {
+ /* New message, alloc head skb */
head = alloc_skb(0, sk->sk_allocation);
- }
+ while (!head) {
+ kcm_push(kcm);
+ err = sk_stream_wait_memory(sk, &timeo);
+ if (err)
+ goto out_error;
- skb = head;
+ head = alloc_skb(0, sk->sk_allocation);
+ }
- /* Set ip_summed to CHECKSUM_UNNECESSARY to avoid calling
- * csum_and_copy_from_iter from skb_do_copy_data_nocache.
- */
- skb->ip_summed = CHECKSUM_UNNECESSARY;
+ skb = head;
+
+ /* Set ip_summed to CHECKSUM_UNNECESSARY to avoid calling
+ * csum_and_copy_from_iter from skb_do_copy_data_nocache.
+ */
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
+ }
start:
while (msg_data_left(msg)) {
@@ -1018,10 +1020,12 @@ wait_for_memory:
if (eor) {
bool not_busy = skb_queue_empty(&sk->sk_write_queue);
- /* Message complete, queue it on send buffer */
- __skb_queue_tail(&sk->sk_write_queue, head);
- kcm->seq_skb = NULL;
- KCM_STATS_INCR(kcm->stats.tx_msgs);
+ if (head) {
+ /* Message complete, queue it on send buffer */
+ __skb_queue_tail(&sk->sk_write_queue, head);
+ kcm->seq_skb = NULL;
+ KCM_STATS_INCR(kcm->stats.tx_msgs);
+ }
if (msg->msg_flags & MSG_BATCH) {
kcm->tx_wait_more = true;
Patches currently in stable-queue which might be from xiyou.wangcong@xxxxxxxxx are
queue-4.9/kcm-fix-0-length-case-for-kcm_sendmsg.patch
queue-4.9/kcm-fix-a-null-pointer-dereference-in-kcm_sendmsg.patch