Handle extra internal fds passed ini recvmsg() (4f459618) · Commits · hpc / gekkofs

src/client/intercept.cpp

+39 −0

Original line number	Diff line number	Diff line
		@@ -21,6 +21,8 @@
		#include <syscall.h>
		#include <errno.h>
		#include <boost/optional.hpp>
		#include <sys/types.h>
		#include <sys/socket.h>

		#include <printf.h>

		@@ -303,6 +305,43 @@ hook_internal(long syscall_number,
		}
		break;

		case SYS_recvmsg:
		{
		*result = syscall_no_intercept(syscall_number,
		static_cast<int>(arg0),
		reinterpret_cast<struct msghdr*>(arg1),
		static_cast<int>(arg2));

		// The recvmsg() syscall can receive file descriptors from another
		// process that the kernel automatically adds to the client's fds
		// as if dup2 had been called. Whenever that happens, we need to
		// make sure that we register these additional fds as internal, or
		// we could inadvertently overwrite them
		if(*result >= 0) {
		auto* hdr = reinterpret_cast<struct msghdr*>(arg1);
		struct cmsghdr* cmsg = CMSG_FIRSTHDR(hdr);

		for(; cmsg != NULL; cmsg = CMSG_NXTHDR(hdr, cmsg)) {
		if(cmsg->cmsg_type == SCM_RIGHTS) {

		size_t nfd = cmsg->cmsg_len > CMSG_LEN(0) ?
		(cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int) :
		0;

		const int* fds =
		reinterpret_cast<int*>(CMSG_DATA(cmsg));

		for(size_t i = 0; i < nfd; ++i) {
		LOG(DEBUG, "recvmsg() provided extra fd {}", fds[i]);
		CTX->register_internal_fd(fds[i]);
		}
		}
		}
		}

		break;
		}

		case SYS_accept:
		*result = syscall_no_intercept(syscall_number,
		static_cast<int>(arg0),