This refactors existing code to close file descriptors in the recovery process, and also adds code to close file descriptors between the fork() and exec() of QEMU or User-Mode Linux. The reason is to avoid leaking main process file descriptors where the main process (or other libraries in the main process) are not setting O_CLOEXEC at all or not setting it atomically. Python is a particular culprit. See also this OpenStack Nova bug report: https://bugs.launchpad.net/nova/+bug/1313477 Thanks: Qin Zhao for identifying and characterizing the problem in Nova. This is version 2 of this commit. This commit is identical to the reverted commit 115fcc34325f965ac3723683e4462fc667dcd254 except that we don't close stderr. --- src/guestfs-internal-frontend.h | 16 +++++++++++++++- src/launch-direct.c | 17 +++++++++-------- src/launch-uml.c | 13 +++++-------- 3 files changed, 29 insertions(+), 17 deletions(-) diff --git a/src/guestfs-internal-frontend.h b/src/guestfs-internal-frontend.h index acd7be5..1e59ad1 100644 --- a/src/guestfs-internal-frontend.h +++ b/src/guestfs-internal-frontend.h @@ -1,5 +1,5 @@ /* libguestfs - * Copyright (C) 2013 Red Hat Inc. + * Copyright (C) 2013-2014 Red Hat Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -164,4 +164,18 @@ extern GUESTFS_DLL_PUBLIC int guestfs___add_libvirt_dom (guestfs_h *g, virDomain # define program_name "libguestfs" #endif +/* Close all file descriptors matching the condition. */ +#define close_file_descriptors(cond) do { \ + int max_fd = sysconf (_SC_OPEN_MAX); \ + int fd; \ + if (max_fd == -1) \ + max_fd = 1024; \ + if (max_fd > 65536) \ + max_fd = 65536; /* bound the amount of work we do here */ \ + for (fd = 0; fd < max_fd; ++fd) { \ + if (cond) \ + close (fd); \ + } \ + } while (0) + #endif /* GUESTFS_INTERNAL_FRONTEND_H_ */ diff --git a/src/launch-direct.c b/src/launch-direct.c index 3de869b..0c3589b 100644 --- a/src/launch-direct.c +++ b/src/launch-direct.c @@ -717,6 +717,13 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) goto dup_failed; close (sv[1]); + + /* Close any other file descriptors that we don't want to pass + * to qemu. This prevents file descriptors which didn't have + * O_CLOEXEC set properly from leaking into the subprocess. See + * RHBZ#1123007. + */ + close_file_descriptors (fd > 2); } /* Dump the command line (after setting up stderr above). */ @@ -747,7 +754,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) if (g->recovery_proc) { r = fork (); if (r == 0) { - int i, fd, max_fd; + int i; struct sigaction sa; pid_t qemu_pid = data->pid; pid_t parent_pid = getppid (); @@ -767,13 +774,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg) /* Close all other file descriptors. This ensures that we don't * hold open (eg) pipes from the parent process. */ - max_fd = sysconf (_SC_OPEN_MAX); - if (max_fd == -1) - max_fd = 1024; - if (max_fd > 65536) - max_fd = 65536; /* bound the amount of work we do here */ - for (fd = 0; fd < max_fd; ++fd) - close (fd); + close_file_descriptors (1); /* It would be nice to be able to put this in the same process * group as qemu (ie. setpgid (0, qemu_pid)). However this is diff --git a/src/launch-uml.c b/src/launch-uml.c index 2a6ddaf..21525e3 100644 --- a/src/launch-uml.c +++ b/src/launch-uml.c @@ -333,6 +333,9 @@ launch_uml (guestfs_h *g, void *datav, const char *arg) goto dup_failed; close (csv[1]); + + /* RHBZ#1123007 */ + close_file_descriptors (fd > 2 && fd != dsv[1]); } /* Dump the command line (after setting up stderr above). */ @@ -360,7 +363,7 @@ launch_uml (guestfs_h *g, void *datav, const char *arg) if (g->recovery_proc) { r = fork (); if (r == 0) { - int i, fd, max_fd; + int i; struct sigaction sa; pid_t vmlinux_pid = data->pid; pid_t parent_pid = getppid (); @@ -380,13 +383,7 @@ launch_uml (guestfs_h *g, void *datav, const char *arg) /* Close all other file descriptors. This ensures that we don't * hold open (eg) pipes from the parent process. */ - max_fd = sysconf (_SC_OPEN_MAX); - if (max_fd == -1) - max_fd = 1024; - if (max_fd > 65536) - max_fd = 65536; /* bound the amount of work we do here */ - for (fd = 0; fd < max_fd; ++fd) - close (fd); + close_file_descriptors (1); /* It would be nice to be able to put this in the same process * group as vmlinux (ie. setpgid (0, vmlinux_pid)). However -- 1.9.0