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kcm: fix a socket double free

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Dmitry reported a double free on kcm socket, which could
be easily reproduced by:

	#include <unistd.h>
	#include <sys/syscall.h>

	int main()
	{
	  int fd = syscall(SYS_socket, 0x29ul, 0x5ul, 0x0ul, 0, 0, 0);
	  syscall(SYS_ioctl, fd, 0x89e2ul, 0x20a98000ul, 0, 0, 0);
	  return 0;
	}

This is because on the error path, after we install
the new socket file, we call sock_release() to clean
up the socket, which leaves the fd pointing to a freed
socket. Fix this by calling sys_close() on that fd
directly.

Fixes: ab7ac4eb98 ("kcm: Kernel Connection Multiplexor module")
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>
This commit is contained in:
WANG Cong 2016-08-28 21:28:26 -07:00 committed by David S. Miller
parent 3b631e52f7
commit c0338aff22
1 changed files with 2 additions and 1 deletions
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3
net/kcm/kcmsock.c
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@ -13,6 +13,7 @@
#include <linux/socket.h>
#include <linux/uaccess.h>
#include <linux/workqueue.h>
#include <linux/syscalls.h>
#include <net/kcm.h>
#include <net/netns/generic.h>
#include <net/sock.h>
@ -2029,7 +2030,7 @@ static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
if (copy_to_user((void __user *)arg, &info,
sizeof(info))) {
err = -EFAULT;
sock_release(newsock);
sys_close(info.fd);
}
}