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authorChristoph Hellwig <hch@lst.de>2020-05-11 13:59:13 +0200
committerDavid S. Miller <davem@davemloft.net>2020-05-11 16:59:16 -0700
commit1f466e1f15cf1dac7c86798d694649fc42cd868a (patch)
tree1f8ca24224e9aa0dbaf924bec224deb08d1ab505 /net/compat.c
parent2618d530dd8b7ac0fdcb83f4c95b88f7b0d37ce6 (diff)
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/compat.c')
-rw-r--r--net/compat.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/compat.c b/net/compat.c
index 4bed96e84d9a..69fc6d1e4e6e 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -56,7 +56,8 @@ int __get_compat_msghdr(struct msghdr *kmsg,
if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
kmsg->msg_namelen = sizeof(struct sockaddr_storage);
- kmsg->msg_control = compat_ptr(msg.msg_control);
+ kmsg->msg_control_is_user = true;
+ kmsg->msg_control_user = compat_ptr(msg.msg_control);
kmsg->msg_controllen = msg.msg_controllen;
if (save_addr)
@@ -121,7 +122,7 @@ int get_compat_msghdr(struct msghdr *kmsg,
((ucmlen) >= sizeof(struct compat_cmsghdr) && \
(ucmlen) <= (unsigned long) \
((mhdr)->msg_controllen - \
- ((char *)(ucmsg) - (char *)(mhdr)->msg_control)))
+ ((char __user *)(ucmsg) - (char __user *)(mhdr)->msg_control_user)))
static inline struct compat_cmsghdr __user *cmsg_compat_nxthdr(struct msghdr *msg,
struct compat_cmsghdr __user *cmsg, int cmsg_len)