5.4-stable review patch. If anyone has any objections, please let me know.
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From: Shigeru Yoshida syoshida@redhat.com
[ Upstream commit c821a88bd720b0046433173185fd841a100d44ad ]
syzbot reported a memory leak like below:
BUG: memory leak unreferenced object 0xffff88810b088c00 (size 240): comm "syz-executor186", pid 5012, jiffies 4294943306 (age 13.680s) hex dump (first 32 bytes): 00 89 08 0b 81 88 ff ff 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: [<ffffffff83e5d5ff>] __alloc_skb+0x1ef/0x230 net/core/skbuff.c:634 [<ffffffff84606e59>] alloc_skb include/linux/skbuff.h:1289 [inline] [<ffffffff84606e59>] kcm_sendmsg+0x269/0x1050 net/kcm/kcmsock.c:815 [<ffffffff83e479c6>] sock_sendmsg_nosec net/socket.c:725 [inline] [<ffffffff83e479c6>] sock_sendmsg+0x56/0xb0 net/socket.c:748 [<ffffffff83e47f55>] ____sys_sendmsg+0x365/0x470 net/socket.c:2494 [<ffffffff83e4c389>] ___sys_sendmsg+0xc9/0x130 net/socket.c:2548 [<ffffffff83e4c536>] __sys_sendmsg+0xa6/0x120 net/socket.c:2577 [<ffffffff84ad7bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff84ad7bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
In kcm_sendmsg(), kcm_tx_msg(head)->last_skb is used as a cursor to append newly allocated skbs to 'head'. If some bytes are copied, an error occurred, and jumped to out_error label, 'last_skb' is left unmodified. A later kcm_sendmsg() will use an obsoleted 'last_skb' reference, corrupting the 'head' frag_list and causing the leak.
This patch fixes this issue by properly updating the last allocated skb in 'last_skb'.
Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Reported-and-tested-by: syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6f98de741f7dbbfc4ccb Signed-off-by: Shigeru Yoshida syoshida@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/kcm/kcmsock.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index 50bcfc71389ab..8668348aa3f2b 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1075,6 +1075,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (head != kcm->seq_skb) kfree_skb(head); + else if (copied) + kcm_tx_msg(head)->last_skb = skb;
err = sk_stream_error(sk, msg->msg_flags, err);