From 027c685e9cb8bc1e0d9774b6db5d47707df8d208 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Thu, 5 Jun 2025 07:57:20 +0000 Subject: [PATCH] Revert "coredump: hand a pidfd to the usermode coredump helper" This reverts commit 79bf58c7c4b7e351331f0344359307836452e70c which is commit b5325b2a270fcaf7b2a9a0f23d422ca8a5a8bdea upstream. It breaks the Android kernel abi and can be brought back in the future in an abi-safe way if it is really needed. Bug: 161946584 Change-Id: I6383f380fc1ad663544a3ddb154b193aa0e4eda3 Signed-off-by: Greg Kroah-Hartman --- fs/coredump.c | 77 ++++------------------------------------- include/linux/binfmts.h | 1 - 2 files changed, 7 insertions(+), 71 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 615e3231a96b..216b7b24fefd 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -52,13 +52,6 @@ #include -/* - * 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 - int core_uses_pid; unsigned int core_pipe_limit; char core_pattern[CORENAME_MAX_SIZE] = "core"; @@ -321,27 +314,6 @@ 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; } @@ -565,7 +537,7 @@ static void wait_for_dump_helpers(struct file *file) } /* - * umh_coredump_setup + * umh_pipe_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) @@ -575,62 +547,27 @@ static void wait_for_dump_helpers(struct file *file) * is a special value that we use to trap recursive * core dumps */ -static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) +static int umh_pipe_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; - 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) - goto out_fail; + return err; cp->file = files[1]; err = replace_fd(0, files[0], 0); fput(files[0]); if (err < 0) - goto out_fail; + return err; /* 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; + return 0; } void do_coredump(const kernel_siginfo_t *siginfo) @@ -706,7 +643,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) } if (cprm.limit == 1) { - /* See umh_coredump_setup() which sets RLIMIT_CORE = 1. + /* See umh_pipe_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 @@ -751,7 +688,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) retval = -ENOMEM; sub_info = call_usermodehelper_setup(helper_argv[0], helper_argv, NULL, GFP_KERNEL, - umh_coredump_setup, NULL, &cprm); + umh_pipe_setup, NULL, &cprm); if (sub_info) retval = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC); diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 1fddc6da9031..b40fc633f3be 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -87,7 +87,6 @@ struct coredump_params { unsigned long mm_flags; loff_t written; loff_t pos; - struct pid *pid; }; /*