[PATCH] uml: preserve errno in error paths

The poster child for this patch is the third tuntap_user hunk.  When an ioctl
fails, it properly closes the opened file descriptor and returns.  However,
the close resets errno to 0, and the 'return errno' that follows returns 0
rather than the value that ioctl set.  This caused the caller to believe that
the device open succeeded and had opened file descriptor 0, which caused no
end of interesting behavior.

The rest of this patch is a pass through the UML sources looking for places
where errno could be reset before being passed back out.  A common culprit is
printk, which could call write, being called before errno is returned.

In some cases, where the code ends up being much smaller, I just deleted the
printk.

There was another case where a caller of run_helper looked at errno after a
failure, rather than the return value of run_helper, which was the errno value
that it wanted.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 39 insertions, 56 deletions

diff --git a/arch/um/os-Linux/aio.c b/arch/um/os-Linux/aio.c
index 182905b..e942beb 100644
--- a/arch/um/os-Linux/aio.c
+++ b/arch/um/os-Linux/aio.c
@@ -313,15 +313,16 @@ static int init_aio_26(void)
         int err;
 
         if(io_setup(256, &ctx)){
+		err = -errno;
                 printk("aio_thread failed to initialize context, err = %d\n",
                        errno);
-                return -errno;
+                return err;
         }
 
         err = run_helper_thread(aio_thread, NULL,
                                 CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
         if(err < 0)
-                return -errno;
+                return err;
 
         aio_pid = err;
 
diff --git a/arch/um/os-Linux/drivers/tuntap_user.c b/arch/um/os-Linux/drivers/tuntap_user.c
index 4b83c6c..4ba9b17 100644
--- a/arch/um/os-Linux/drivers/tuntap_user.c
+++ b/arch/um/os-Linux/drivers/tuntap_user.c
@@ -75,7 +75,7 @@ static int tuntap_open_tramp(char *gate, int *fd_out, int me, int remote,
 	struct msghdr msg;
 	struct cmsghdr *cmsg;
 	struct iovec iov;
-	int pid, n;
+	int pid, n, err;
 
 	sprintf(version_buf, "%d", UML_NET_VERSION);
 
@@ -105,9 +105,10 @@ static int tuntap_open_tramp(char *gate, int *fd_out, int me, int remote,
 	n = recvmsg(me, &msg, 0);
 	*used_out = n;
 	if(n < 0){
+		err = -errno;
 		printk("tuntap_open_tramp : recvmsg failed - errno = %d\n", 
 		       errno);
-		return(-errno);
+		return err;
 	}
 	CATCH_EINTR(waitpid(pid, NULL, 0));
 
@@ -147,9 +148,10 @@ static int tuntap_open(void *data)
 		ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
 		strlcpy(ifr.ifr_name, pri->dev_name, sizeof(ifr.ifr_name));
 		if(ioctl(pri->fd, TUNSETIFF, (void *) &ifr) < 0){
+			err = -errno;
 			printk("TUNSETIFF failed, errno = %d\n", errno);
 			os_close_file(pri->fd);
-			return(-errno);
+			return err;
 		}
 	}
 	else {
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index fd45bb2..f55773c 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -119,15 +119,11 @@ int os_window_size(int fd, int *rows, int *cols)
 
 int os_new_tty_pgrp(int fd, int pid)
 {
-	if(ioctl(fd, TIOCSCTTY, 0) < 0){
-		printk("TIOCSCTTY failed, errno = %d\n", errno);
-		return(-errno);
-	}
+	if(ioctl(fd, TIOCSCTTY, 0) < 0)
+		return -errno;
 
-	if(tcsetpgrp(fd, pid) < 0){
-		printk("tcsetpgrp failed, errno = %d\n", errno);
-		return(-errno);
-	}
+	if(tcsetpgrp(fd, pid) < 0)
+		return -errno;
 
 	return(0);
 }
@@ -146,18 +142,12 @@ int os_set_slip(int fd)
 	int disc, sencap;
 
 	disc = N_SLIP;
-	if(ioctl(fd, TIOCSETD, &disc) < 0){
-		printk("Failed to set slip line discipline - "
-		       "errno = %d\n", errno);
-		return(-errno);
-	}
+	if(ioctl(fd, TIOCSETD, &disc) < 0)
+		return -errno;
 
 	sencap = 0;
-	if(ioctl(fd, SIOCSIFENCAP, &sencap) < 0){
-		printk("Failed to set slip encapsulation - "
-		       "errno = %d\n", errno);
-		return(-errno);
-	}
+	if(ioctl(fd, SIOCSIFENCAP, &sencap) < 0)
+		return -errno;
 
 	return(0);
 }
@@ -180,22 +170,15 @@ int os_sigio_async(int master, int slave)
 	int flags;
 
 	flags = fcntl(master, F_GETFL);
-	if(flags < 0) {
-		printk("fcntl F_GETFL failed, errno = %d\n", errno);
-		return(-errno);
-	}
+	if(flags < 0)
+		return errno;
 
 	if((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
-	   (fcntl(master, F_SETOWN, os_getpid()) < 0)){
-		printk("fcntl F_SETFL or F_SETOWN failed, errno = %d\n",
-		       errno);
-		return(-errno);
-	}
+	   (fcntl(master, F_SETOWN, os_getpid()) < 0))
+		return -errno;
 
-	if((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0)){
-		printk("fcntl F_SETFL failed, errno = %d\n", errno);
-		return(-errno);
-	}
+	if((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
+		return -errno;
 
 	return(0);
 }
@@ -255,7 +238,7 @@ int os_file_mode(char *file, struct openflags *mode_out)
 
 int os_open_file(char *file, struct openflags flags, int mode)
 {
-	int fd, f = 0;
+	int fd, err, f = 0;
 
 	if(flags.r && flags.w) f = O_RDWR;
 	else if(flags.r) f = O_RDONLY;
@@ -272,8 +255,9 @@ int os_open_file(char *file, struct openflags flags, int mode)
 		return(-errno);
 
 	if(flags.cl && fcntl(fd, F_SETFD, 1)){
+		err = -errno;
 		os_close_file(fd);
-		return(-errno);
+		return err;
 	}
 
 	return(fd);
@@ -383,9 +367,9 @@ int os_file_size(char *file, unsigned long long *size_out)
 			return(fd);
 		}
 		if(ioctl(fd, BLKGETSIZE, &blocks) < 0){
+			err = -errno;
 			printk("Couldn't get the block size of \"%s\", "
 			       "errno = %d\n", file, errno);
-			err = -errno;
 			os_close_file(fd);
 			return(err);
 		}
@@ -473,11 +457,14 @@ int os_pipe(int *fds, int stream, int close_on_exec)
 
 int os_set_fd_async(int fd, int owner)
 {
+	int err;
+
 	/* XXX This should do F_GETFL first */
 	if(fcntl(fd, F_SETFL, O_ASYNC | O_NONBLOCK) < 0){
+		err = -errno;
 		printk("os_set_fd_async : failed to set O_ASYNC and "
 		       "O_NONBLOCK on fd # %d, errno = %d\n", fd, errno);
-		return(-errno);
+		return err;
 	}
 #ifdef notdef
 	if(fcntl(fd, F_SETFD, 1) < 0){
@@ -488,10 +475,11 @@ int os_set_fd_async(int fd, int owner)
 
 	if((fcntl(fd, F_SETSIG, SIGIO) < 0) ||
 	   (fcntl(fd, F_SETOWN, owner) < 0)){
+		err = -errno;
 		printk("os_set_fd_async : Failed to fcntl F_SETOWN "
 		       "(or F_SETSIG) fd %d to pid %d, errno = %d\n", fd, 
 		       owner, errno);
-		return(-errno);
+		return err;
 	}
 
 	return(0);
@@ -516,11 +504,9 @@ int os_set_fd_block(int fd, int blocking)
 	if(blocking) flags &= ~O_NONBLOCK;
 	else flags |= O_NONBLOCK;
 
-	if(fcntl(fd, F_SETFL, flags) < 0){
-		printk("Failed to change blocking on fd # %d, errno = %d\n",
-		       fd, errno);
-		return(-errno);
-	}
+	if(fcntl(fd, F_SETFL, flags) < 0)
+		return -errno;
+
 	return(0);
 }
 
@@ -609,11 +595,8 @@ int os_create_unix_socket(char *file, int len, int close_on_exec)
 	int sock, err;
 
 	sock = socket(PF_UNIX, SOCK_DGRAM, 0);
-	if (sock < 0){
-		printk("create_unix_socket - socket failed, errno = %d\n",
-		       errno);
-		return(-errno);
-	}
+	if(sock < 0)
+		return -errno;
 
 	if(close_on_exec) {
 		err = os_set_exec_close(sock, 1);
@@ -628,11 +611,8 @@ int os_create_unix_socket(char *file, int len, int close_on_exec)
 	snprintf(addr.sun_path, len, "%s", file);
 
 	err = bind(sock, (struct sockaddr *) &addr, sizeof(addr));
-	if (err < 0){
-		printk("create_listening_socket at '%s' - bind failed, "
-		       "errno = %d\n", file, errno);
-		return(-errno);
-	}
+	if(err < 0)
+		return -errno;
 
 	return(sock);
 }