This patchset fixes some problems in conversions of cmsg structures
in target_to_host_cmsg() (used in send/recvmsg handling). Specifically:
* we required the msg->msg_controllen to declare the buffer
to have enough space for final trailing padding (we were
checking against CMSG_SPACE), whereas the kernel does not
require this, and common userspace code assumes this.
* we weren't correctly handling the fact that the SO_TIMESTAMP
payload may be larger for the target than the host
* we weren't marking the messages with MSG_CTRUNC when we did
need to truncate a message that wasn't truncated by the host,
but were instead logging a QEMU message; since truncation is
always the result of a guest giving us an insufficiently
sized buffer, we should report it to the guest as the kernel
does and don't log anything
* we weren't handling the possibility of the host having a
more restrictive alignment requirement for payload structs
The major visible issue I wanted to fix is that glibc's "try to talk
to nscd" code that it will run on startup will receive a cmsg with a
4 byte payload and only allocates 4 bytes for it, which was causing
us to do the wrong thing on architectures that need 8-alignment
(we dropped the cmsg and printed a diagnostic message).
Peter Maydell (2):
linux-user: Fix length handling in host_to_target_cmsg
linux-user: use __get_user and __put_user in cmsg conversions
linux-user/syscall.c | 89 ++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 72 insertions(+), 17 deletions(-)
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1.9.1
