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linux-user: Allow bad msg_name for recvfrom on connected socket 

The POSIX standard mandates that for a connected socket recvfrom()
must ignore the msg_name and msg_namelen fields. This is awkward
for QEMU because we will attempt to copy them from guest address
space. Handle this by not immediately returning a TARGET_EFAULT
if the copy failed, but instead passing a known-bad address
to the host kernel, which can then return EFAULT or ignore the
value appropriately.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Peter Maydell 2016-07-15 14:57:28 +01:00 committed by Riku Voipio
parent 97b0797033
commit 26a6fc96e0
1 changed files with 9 additions and 2 deletions
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11
linux-user/syscall.c
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@ -3472,7 +3472,14 @@ static abi_long do_sendrecvmsg_locked(int fd, struct target_msghdr *msgp,
ret = target_to_host_sockaddr(fd, msg.msg_name,
tswapal(msgp->msg_name),
msg.msg_namelen);
if (ret) {
if (ret == -TARGET_EFAULT) {
/* For connected sockets msg_name and msg_namelen must
* be ignored, so returning EFAULT immediately is wrong.
* Instead, pass a bad msg_name to the host kernel, and
* let it decide whether to return EFAULT or not.
*/
msg.msg_name = (void *)-1;
} else if (ret) {
goto out2;
}
} else {
@ -3534,7 +3541,7 @@ static abi_long do_sendrecvmsg_locked(int fd, struct target_msghdr *msgp,
}
if (!is_error(ret)) {
msgp->msg_namelen = tswap32(msg.msg_namelen);
if (msg.msg_name != NULL) {
if (msg.msg_name != NULL && msg.msg_name != (void *)-1) {
ret = host_to_target_sockaddr(tswapal(msgp->msg_name),
msg.msg_name, msg.msg_namelen);
if (ret) {