diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp index 3207b3c6f1871..d1fe07bcc779d 100644 --- a/core/jni/com_android_internal_os_Zygote.cpp +++ b/core/jni/com_android_internal_os_Zygote.cpp @@ -454,6 +454,10 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra SetForkLoad(true); #endif + // Close any logging related FDs before we start evaluating the list of + // file descriptors. + __android_log_close(); + // If this is the first fork for this zygote, create the open FD table. // If it isn't, we just need to check whether the list of open files has // changed (and it shouldn't in the normal case). @@ -477,7 +481,7 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra // Re-open all remaining open file descriptors so that they aren't shared // with the zygote across a fork. - if (!gOpenFdTable->Reopen()) { + if (!gOpenFdTable->ReopenOrDetach()) { RuntimeAbort(env, __LINE__, "Unable to reopen whitelisted descriptors."); } diff --git a/core/jni/fd_utils-inl.h b/core/jni/fd_utils-inl.h index 1f34b0275384e..c836b349dc725 100644 --- a/core/jni/fd_utils-inl.h +++ b/core/jni/fd_utils-inl.h @@ -25,22 +25,32 @@ #include #include #include +#include #include #include +#include #include #include #include "JNIHelp.h" #include "ScopedPrimitiveArray.h" -// Whitelist of open paths that the zygote is allowed to keep open -// that will be recreated across forks. In addition to files here, -// all files ending with ".jar" under /system/framework" are -// whitelisted. See FileDescriptorInfo::IsWhitelisted for the -// canonical definition. +// Whitelist of open paths that the zygote is allowed to keep open. +// +// In addition to the paths listed here, all files ending with +// ".jar" under /system/framework" are whitelisted. See +// FileDescriptorInfo::IsWhitelisted for the canonical definition. +// +// If the whitelisted path is associated with a regular file or a +// character device, the file is reopened after a fork with the same +// offset and mode. If the whilelisted path is associated with a +// AF_UNIX socket, the socket will refer to /dev/null after each +// fork, and all operations on it will fail. static const char* kPathWhitelist[] = { "/dev/null", "/dev/pmsg0", + "/dev/socket/zygote", + "/dev/socket/zygote_secondary", "/system/etc/event-log-tags", "/sys/kernel/debug/tracing/trace_marker", "/system/framework/framework-res.apk", @@ -65,9 +75,17 @@ class FileDescriptorInfo { return NULL; } - // Ignore (don't reopen or fail on) socket fds for now. if (S_ISSOCK(f_stat.st_mode)) { - ALOGW("Unsupported socket FD: %d, ignoring.", fd); + std::string socket_name; + if (!GetSocketName(fd, &socket_name)) { + return NULL; + } + + if (!IsWhitelisted(socket_name)) { + ALOGE("Socket name not whitelisted : %s (fd=%d)", socket_name.c_str(), fd); + return NULL; + } + return new FileDescriptorInfo(fd); } @@ -146,10 +164,9 @@ class FileDescriptorInfo { return f_stat.st_ino == stat.st_ino && f_stat.st_dev == stat.st_dev; } - bool Reopen() const { - // Always skip over socket FDs for now. + bool ReopenOrDetach() const { if (is_sock) { - return true; + return DetachSocket(); } // NOTE: This might happen if the file was unlinked after being opened. @@ -186,9 +203,7 @@ class FileDescriptorInfo { return false; } - if (close(new_fd) == -1) { - ALOGW("Failed close(%d) : %s", new_fd, strerror(errno)); - } + close(new_fd); return true; } @@ -264,6 +279,74 @@ class FileDescriptorInfo { return true; } + // Returns the locally-bound name of the socket |fd|. Returns true + // iff. all of the following hold : + // + // - the socket's sa_family is AF_UNIX. + // - the length of the path is greater than zero (i.e, not an unnamed socket). + // - the first byte of the path isn't zero (i.e, not a socket with an abstract + // address). + static bool GetSocketName(const int fd, std::string* result) { + sockaddr_storage ss; + sockaddr* addr = reinterpret_cast(&ss); + socklen_t addr_len = sizeof(ss); + + if (TEMP_FAILURE_RETRY(getsockname(fd, addr, &addr_len)) == -1) { + ALOGE("Failed getsockname(%d) : %s", fd, strerror(errno)); + return false; + } + + if (addr->sa_family != AF_UNIX) { + ALOGE("Unsupported socket (fd=%d) with family %d", fd, addr->sa_family); + return false; + } + + const sockaddr_un* unix_addr = reinterpret_cast(&ss); + + size_t path_len = addr_len - offsetof(struct sockaddr_un, sun_path); + // This is an unnamed local socket, we do not accept it. + if (path_len == 0) { + ALOGE("Unsupported AF_UNIX socket (fd=%d) with empty path.", fd); + return false; + } + + // This is a local socket with an abstract address, we do not accept it. + if (unix_addr->sun_path[0] == '\0') { + ALOGE("Unsupported AF_UNIX socket (fd=%d) with abstract address.", fd); + return false; + } + + // If we're here, sun_path must refer to a null terminated filesystem + // pathname (man 7 unix). Remove the terminator before assigning it to an + // std::string. + if (unix_addr->sun_path[path_len - 1] == '\0') { + --path_len; + } + + result->assign(unix_addr->sun_path, path_len); + return true; + } + + bool DetachSocket() const { + const int dev_null_fd = open("/dev/null", O_RDWR); + if (dev_null_fd < 0) { + ALOGE("Failed to open /dev/null : %s", strerror(errno)); + return false; + } + + if (dup2(dev_null_fd, fd) == -1) { + ALOGE("Failed dup2 on socket descriptor %d : %s", fd, strerror(errno)); + return false; + } + + if (close(dev_null_fd) == -1) { + ALOGE("Failed close(%d) : %s", dev_null_fd, strerror(errno)); + return false; + } + + return true; + } + DISALLOW_COPY_AND_ASSIGN(FileDescriptorInfo); }; @@ -337,12 +420,13 @@ class FileDescriptorTable { } // Reopens all file descriptors that are contained in the table. Returns true - // if all descriptors were re-opened, and false if an error occurred. - bool Reopen() { + // if all descriptors were successfully re-opened or detached, and false if an + // error occurred. + bool ReopenOrDetach() { std::unordered_map::const_iterator it; for (it = open_fd_map_.begin(); it != open_fd_map_.end(); ++it) { const FileDescriptorInfo* info = it->second; - if (info == NULL || !info->Reopen()) { + if (info == NULL || !info->ReopenOrDetach()) { return false; } } @@ -373,7 +457,7 @@ class FileDescriptorTable { // // TODO(narayan): This will be an error in a future android release. // error = true; - ALOGW("Zygote closed file descriptor %d.", it->first); + // ALOGW("Zygote closed file descriptor %d.", it->first); open_fd_map_.erase(it); } else { // The entry from the file descriptor table is still open. Restat @@ -404,7 +488,7 @@ class FileDescriptorTable { // // TODO(narayan): This will be an error in a future android release. // error = true; - ALOGW("Zygote opened %zd new file descriptor(s).", open_fds.size()); + // ALOGW("Zygote opened %zd new file descriptor(s).", open_fds.size()); // TODO(narayan): This code will be removed in a future android release. std::set::const_iterator it;