diff options
Diffstat (limited to 'fs/coredump.c')
| -rw-r--r-- | fs/coredump.c | 81 |
1 files changed, 75 insertions, 6 deletions
diff --git a/fs/coredump.c b/fs/coredump.c index 4d332f147137..b0d782367fcc 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -42,6 +42,7 @@ #include <linux/timekeeping.h> #include <linux/sysctl.h> #include <linux/elf.h> +#include <uapi/linux/pidfd.h> #include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -56,6 +57,13 @@ static bool dump_vma_snapshot(struct coredump_params *cprm); static void free_vma_snapshot(struct coredump_params *cprm); +/* + * File descriptor number for the pidfd for the thread-group leader of + * the coredumping task installed into the usermode helper's file + * descriptor table. + */ +#define COREDUMP_PIDFD_NUMBER 3 + static int core_uses_pid; static unsigned int core_pipe_limit; static char core_pattern[CORENAME_MAX_SIZE] = "core"; @@ -325,6 +333,27 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm, err = cn_printf(cn, "%lu", rlimit(RLIMIT_CORE)); break; + /* pidfd number */ + case 'F': { + /* + * Installing a pidfd only makes sense if + * we actually spawn a usermode helper. + */ + if (!ispipe) + break; + + /* + * Note that we'll install a pidfd for the + * thread-group leader. We know that task + * linkage hasn't been removed yet and even if + * this @current isn't the actual thread-group + * leader we know that the thread-group leader + * cannot be reaped until @current has exited. + */ + cprm->pid = task_tgid(current); + err = cn_printf(cn, "%d", COREDUMP_PIDFD_NUMBER); + break; + } default: break; } @@ -479,7 +508,7 @@ static void wait_for_dump_helpers(struct file *file) } /* - * umh_pipe_setup + * umh_coredump_setup * helper function to customize the process used * to collect the core in userspace. Specifically * it sets up a pipe and installs it as fd 0 (stdin) @@ -489,21 +518,61 @@ static void wait_for_dump_helpers(struct file *file) * is a special value that we use to trap recursive * core dumps */ -static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) +static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) { struct file *files[2]; + struct file *pidfs_file = NULL; struct coredump_params *cp = (struct coredump_params *)info->data; - int err = create_pipe_files(files, 0); + int err; + + if (cp->pid) { + int fd; + + fd = pidfd_prepare(cp->pid, 0, &pidfs_file); + if (fd < 0) + return fd; + + /* + * We don't care about the fd. We also cannot simply + * replace it below because dup2() will refuse to close + * this file descriptor if its in a larval state. So + * close it! + */ + put_unused_fd(fd); + + /* + * Usermode helpers are childen of either + * system_unbound_wq or of kthreadd. So we know that + * we're starting off with a clean file descriptor + * table. So we should always be able to use + * COREDUMP_PIDFD_NUMBER as our file descriptor value. + */ + err = replace_fd(COREDUMP_PIDFD_NUMBER, pidfs_file, 0); + if (err < 0) + goto out_fail; + + pidfs_file = NULL; + } + + err = create_pipe_files(files, 0); if (err) - return err; + goto out_fail; cp->file = files[1]; err = replace_fd(0, files[0], 0); fput(files[0]); + if (err < 0) + goto out_fail; + /* and disallow core files too */ current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; + err = 0; + +out_fail: + if (pidfs_file) + fput(pidfs_file); return err; } @@ -580,7 +649,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) } if (cprm.limit == 1) { - /* See umh_pipe_setup() which sets RLIMIT_CORE = 1. + /* See umh_coredump_setup() which sets RLIMIT_CORE = 1. * * Normally core limits are irrelevant to pipes, since * we're not writing to the file system, but we use @@ -625,7 +694,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) retval = -ENOMEM; sub_info = call_usermodehelper_setup(helper_argv[0], helper_argv, NULL, GFP_KERNEL, - umh_pipe_setup, NULL, &cprm); + umh_coredump_setup, NULL, &cprm); if (sub_info) retval = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC); |