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authorWANG Cong <xiyou.wangcong@gmail.com>2017-02-07 23:59:47 +0300
committerDavid S. Miller <davem@davemloft.net>2017-02-10 00:38:48 +0300
commit98e3862ca2b1ae595a13805dcab4c3a6d7718f4d (patch)
tree52879528ae93a9cc7aec463a1f1d1653c3da967f /net
parent538d92912d3190a1dd809233a0d57277459f37b2 (diff)
downloadlinux-98e3862ca2b1ae595a13805dcab4c3a6d7718f4d.tar.xz
kcm: fix 0-length case for kcm_sendmsg()
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@google.com> Cc: Tom Herbert <tom@herbertland.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/kcm/kcmsock.c40
1 files changed, 22 insertions, 18 deletions
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 7e08a4d3d77d..64f0e8531af0 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -929,23 +929,25 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
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;