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authorBreno Leitao <leitao@debian.org>2023-06-09 08:27:42 -0700
committerJakub Kicinski <kuba@kernel.org>2023-06-15 22:33:26 -0700
commite1d001fa5b477c4da46a29be1fcece91db7c7c6f (patch)
tree4831d11ee879f6ac20d4ad6a6435c5c753ff5849 /net/dccp/dccp.h
parent173780ff18a93298ca84224cc79df69f9cc198ce (diff)
net: ioctl: Use kernel memory on protocol ioctl callbacks
Most of the ioctls to net protocols operates directly on userspace argument (arg). Usually doing get_user()/put_user() directly in the ioctl callback. This is not flexible, because it is hard to reuse these functions without passing userspace buffers. Change the "struct proto" ioctls to avoid touching userspace memory and operate on kernel buffers, i.e., all protocol's ioctl callbacks is adapted to operate on a kernel memory other than on userspace (so, no more {put,get}_user() and friends being called in the ioctl callback). This changes the "struct proto" ioctl format in the following way: int (*ioctl)(struct sock *sk, int cmd, - unsigned long arg); + int *karg); (Important to say that this patch does not touch the "struct proto_ops" protocols) So, the "karg" argument, which is passed to the ioctl callback, is a pointer allocated to kernel space memory (inside a function wrapper). This buffer (karg) may contain input argument (copied from userspace in a prep function) and it might return a value/buffer, which is copied back to userspace if necessary. There is not one-size-fits-all format (that is I am using 'may' above), but basically, there are three type of ioctls: 1) Do not read from userspace, returns a result to userspace 2) Read an input parameter from userspace, and does not return anything to userspace 3) Read an input from userspace, and return a buffer to userspace. The default case (1) (where no input parameter is given, and an "int" is returned to userspace) encompasses more than 90% of the cases, but there are two other exceptions. Here is a list of exceptions: * Protocol RAW: * cmd = SIOCGETVIFCNT: * input and output = struct sioc_vif_req * cmd = SIOCGETSGCNT * input and output = struct sioc_sg_req * Explanation: for the SIOCGETVIFCNT case, userspace passes the input argument, which is struct sioc_vif_req. Then the callback populates the struct, which is copied back to userspace. * Protocol RAW6: * cmd = SIOCGETMIFCNT_IN6 * input and output = struct sioc_mif_req6 * cmd = SIOCGETSGCNT_IN6 * input and output = struct sioc_sg_req6 * Protocol PHONET: * cmd == SIOCPNADDRESOURCE | SIOCPNDELRESOURCE * input int (4 bytes) * Nothing is copied back to userspace. For the exception cases, functions sock_sk_ioctl_inout() will copy the userspace input, and copy it back to kernel space. The wrapper that prepare the buffer and put the buffer back to user is sk_ioctl(), so, instead of calling sk->sk_prot->ioctl(), the callee now calls sk_ioctl(), which will handle all cases. Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Willem de Bruijn <willemb@google.com> Reviewed-by: David Ahern <dsahern@kernel.org> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://lore.kernel.org/r/20230609152800.830401-1-leitao@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/dccp/dccp.h')
-rw-r--r--net/dccp/dccp.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 9ddc3a9e89e4..1f748ed1279d 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -292,7 +292,7 @@ int dccp_getsockopt(struct sock *sk, int level, int optname,
char __user *optval, int __user *optlen);
int dccp_setsockopt(struct sock *sk, int level, int optname,
sockptr_t optval, unsigned int optlen);
-int dccp_ioctl(struct sock *sk, int cmd, unsigned long arg);
+int dccp_ioctl(struct sock *sk, int cmd, int *karg);
int dccp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
int dccp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags,
int *addr_len);