commit: fcb399f5a685f088b9f10d9d57e326ee78f9e6dd Author: Zac Medico <zmedico <AT> gentoo <DOT> org> AuthorDate: Mon Nov 12 03:56:24 2018 +0000 Commit: Michał Górny <mgorny <AT> gentoo <DOT> org> CommitDate: Sun Dec 2 15:17:39 2018 +0000 URL: https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=fcb399f5
libsandbox: resolve_dirfd_path /proc/<pid> namespace safety If /proc was mounted by a process in a different pid namespace, getpid cannot be used create a valid /proc/<pid> path. Instead use sb_get_fd_dir() which works in any case. This implements option 3 of these choices: 1) Always create a mount namespace when creating a pid namespace, and remount /proc so that /proc/<pid> entries are always consistent with the current pid namespace. 2) Use readlink on /proc/self instead of getpid to determine the pid of self in the pid namespace of the /proc mount. 3) Use /proc/self or /dev/fd directly. Bug: https://bugs.gentoo.org/670966 Signed-off-by: Zac Medico <zmedico <AT> gentoo.org> Closes: https://github.com/gentoo/sandbox/pull/1 Signed-off-by: Michał Górny <mgorny <AT> gentoo.org> libsandbox/libsandbox.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/libsandbox/libsandbox.c b/libsandbox/libsandbox.c index 9ef13b1..e0c9d1a 100644 --- a/libsandbox/libsandbox.c +++ b/libsandbox/libsandbox.c @@ -125,7 +125,14 @@ int resolve_dirfd_path(int dirfd, const char *path, char *resolved_path, save_errno(); size_t at_len = resolved_path_len - 1 - 1 - (path ? strlen(path) : 0); - sprintf(resolved_path, "/proc/%i/fd/%i", trace_pid ? : getpid(), dirfd); + if (trace_pid) + sprintf(resolved_path, "/proc/%i/fd/%i", trace_pid, dirfd); + else + /* If /proc was mounted by a process in a different pid namespace, + * getpid cannot be used to create a valid /proc/<pid> path. Instead + * use sb_get_fd_dir() which works in any case. + */ + sprintf(resolved_path, "%s/%i", sb_get_fd_dir(), dirfd); ssize_t ret = readlink(resolved_path, resolved_path, at_len); if (ret == -1) { /* see comments at end of check_syscall() */
