diff options
author | Christoph Hellwig <hch@lst.de> | 2020-05-11 13:59:13 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2020-05-11 16:59:16 -0700 |
commit | 1f466e1f15cf1dac7c86798d694649fc42cd868a (patch) | |
tree | 1f8ca24224e9aa0dbaf924bec224deb08d1ab505 /net/socket.c | |
parent | 2618d530dd8b7ac0fdcb83f4c95b88f7b0d37ce6 (diff) | |
download | linux-1f466e1f15cf1dac7c86798d694649fc42cd868a.tar.bz2 |
net: cleanly handle kernel vs user buffers for ->msg_control
The msg_control field in struct msghdr can either contain a user
pointer when used with the recvmsg system call, or a kernel pointer
when used with sendmsg. To complicate things further kernel_recvmsg
can stuff a kernel pointer in and then use set_fs to make the uaccess
helpers accept it.
Replace it with a union of a kernel pointer msg_control field, and
a user pointer msg_control_user one, and allow kernel_recvmsg operate
on a proper kernel pointer using a bitfield to override the normal
choice of a user pointer for recvmsg.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/socket.c')
-rw-r--r-- | net/socket.c | 22 |
1 files changed, 6 insertions, 16 deletions
diff --git a/net/socket.c b/net/socket.c index 2dd739fba866..1c9a7260a41d 100644 --- a/net/socket.c +++ b/net/socket.c @@ -924,14 +924,9 @@ EXPORT_SYMBOL(sock_recvmsg); int kernel_recvmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, size_t num, size_t size, int flags) { - mm_segment_t oldfs = get_fs(); - int result; - + msg->msg_control_is_user = false; iov_iter_kvec(&msg->msg_iter, READ, vec, num, size); - set_fs(KERNEL_DS); - result = sock_recvmsg(sock, msg, flags); - set_fs(oldfs); - return result; + return sock_recvmsg(sock, msg, flags); } EXPORT_SYMBOL(kernel_recvmsg); @@ -2239,7 +2234,8 @@ int __copy_msghdr_from_user(struct msghdr *kmsg, if (copy_from_user(&msg, umsg, sizeof(*umsg))) return -EFAULT; - kmsg->msg_control = (void __force *)msg.msg_control; + kmsg->msg_control_is_user = true; + kmsg->msg_control_user = msg.msg_control; kmsg->msg_controllen = msg.msg_controllen; kmsg->msg_flags = msg.msg_flags; @@ -2331,16 +2327,10 @@ static int ____sys_sendmsg(struct socket *sock, struct msghdr *msg_sys, goto out; } err = -EFAULT; - /* - * Careful! Before this, msg_sys->msg_control contains a user pointer. - * Afterwards, it will be a kernel pointer. Thus the compiler-assisted - * checking falls down on this. - */ - if (copy_from_user(ctl_buf, - (void __user __force *)msg_sys->msg_control, - ctl_len)) + if (copy_from_user(ctl_buf, msg_sys->msg_control_user, ctl_len)) goto out_freectl; msg_sys->msg_control = ctl_buf; + msg_sys->msg_control_is_user = false; } msg_sys->msg_flags = flags; |