Properly handle read() and write() throughout the SSSD

We need to guarantee at all times that reads and writes complete
successfully. This means that they must be checked for returning
EINTR and EAGAIN, and all writes must be wrapped in a loop to
ensure that they do not truncate their output.

3 files changed, 57 insertions, 12 deletions

diff --git a/src/util/backup_file.c b/src/util/backup_file.c
index cf9ddf303..990793278 100644
--- a/src/util/backup_file.c
+++ b/src/util/backup_file.c
@@ -86,7 +86,7 @@ int backup_file(const char *src_file, int dbglvl)
     while (1) {
         num = read(src_fd, buf, BUFFER_SIZE);
         if (num < 0) {
-            if (errno == EINTR) continue;
+            if (errno == EINTR || errno == EAGAIN) continue;
             ret = errno;
             DEBUG(dbglvl, ("Error (%d [%s]) reading from source %s\n",
                            ret, strerror(ret), src_file));
@@ -101,7 +101,7 @@ int backup_file(const char *src_file, int dbglvl)
             errno = 0;
             num = write(dst_fd, &buf[pos], count);
             if (num < 0) {
-                if (errno == EINTR) continue;
+                if (errno == EINTR || errno == EAGAIN) continue;
                 ret = errno;
                 DEBUG(dbglvl, ("Error (%d [%s]) writing to destination %s\n",
                                ret, strerror(ret), dst_file));
diff --git a/src/util/find_uid.c b/src/util/find_uid.c
index 965966ef3..952aeea4a 100644
--- a/src/util/find_uid.c
+++ b/src/util/find_uid.c
@@ -100,10 +100,15 @@ static errno_t get_uid_from_pid(const pid_t pid, uid_t *uid)
         DEBUG(1, ("open failed [%d][%s].\n", errno, strerror(errno)));
         return errno;
     }
-    ret = read(fd, buf, BUFSIZE);
-    if (ret == -1) {
-        DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
-        return errno;
+
+    while ((ret = read(fd, buf, BUFSIZE)) != 0) {
+        if (ret == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
+            return errno;
+        }
     }
 
     ret = close(fd);
diff --git a/src/util/server.c b/src/util/server.c
index 007b36241..8f5b44146 100644
--- a/src/util/server.c
+++ b/src/util/server.c
@@ -104,6 +104,10 @@ int pidfile(const char *path, const char *name)
     char *file;
     int fd;
     int ret, err;
+    ssize_t len;
+    ssize_t size;
+    ssize_t written;
+    ssize_t pidlen = sizeof(pid_str - 1);
 
     file = talloc_asprintf(NULL, "%s/%s.pid", path, name);
     if (!file) {
@@ -114,9 +118,30 @@ int pidfile(const char *path, const char *name)
     err = errno;
     if (fd != -1) {
 
-        pid_str[sizeof(pid_str) -1] = '\0';
-        ret = read(fd, pid_str, sizeof(pid_str) -1);
-        if (ret > 0) {
+        pid_str[pidlen] = '\0';
+
+
+        while ((ret = read(fd, pid_str + len, pidlen - len)) != 0) {
+            if (ret == -1) {
+                if (errno == EINTR || errno == EAGAIN) {
+                    continue;
+                }
+                DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
+                break;
+            } else if (ret > 0) {
+                len += ret;
+                if (len > pidlen) {
+                    DEBUG(1, ("read too much, this should never happen.\n"));
+                    break;
+                }
+                continue;
+            } else {
+                DEBUG(1, ("unexpected return code of read [%d].\n", ret));
+                break;
+            }
+        }
+
+        if (ret == 0) {
             /* let's check the pid */
 
             pid = (pid_t)atoi(pid_str);
@@ -159,10 +184,25 @@ int pidfile(const char *path, const char *name)
 
     memset(pid_str, 0, sizeof(pid_str));
     snprintf(pid_str, sizeof(pid_str) -1, "%u\n", (unsigned int) getpid());
+    size = strlen(pid_str);
+
+    written = 0;
+    while (written < size) {
+        ret = write(fd, pid_str+written, size-written);
+        if (ret == -1) {
+            err = errno;
+            if (err == EINTR || err == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("write failed [%d][%s]\n", err, strerror(err)));
+            break;
+        }
+        else {
+            written += ret;
+        }
+    }
 
-    ret = write(fd, pid_str, strlen(pid_str));
-    err = errno;
-    if (ret != strlen(pid_str)) {
+    if (written != size) {
         close(fd);
         return err;
     }