[PATCH v4 02/11] coredump: massage do_coredump()

Christian Brauner
2025-05-07T16:13:55Z

We're going to extend the coredump code in follow-up patches.
Clean it up so we can do this more easily.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
fs/coredump.c | 122 +++++++++++++++++++++++++++++++---------------------------
1 file changed, 65 insertions(+), 57 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 281320ea351f..41491dbfafdf 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -646,63 +646,8 @@ void do_coredump(const kernel_siginfo_t *siginfo)
goto fail_unlock;
}

- if (cn.core_type == COREDUMP_PIPE) {
- int argi;
- int dump_count;
- char **helper_argv;
- struct subprocess_info *sub_info;
-
- if (cprm.limit == 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
- * cprm.limit of 1 here as a special value, this is a
- * consistent way to catch recursive crashes.
- * We can still crash if the core_pattern binary sets
- * RLIM_CORE = !1, but it runs as root, and can do
- * lots of stupid things.
- *
- * Note that we use task_tgid_vnr here to grab the pid
- * of the process group leader. That way we get the
- * right pid if a thread in a multi-threaded
- * core_pattern process dies.
- */
- coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
- goto fail_unlock;
- }
- cprm.limit = RLIM_INFINITY;
-
- dump_count = atomic_inc_return(&core_dump_count);
- if (core_pipe_limit && (core_pipe_limit < dump_count)) {
- coredump_report_failure("over core_pipe_limit, skipping core dump");
- goto fail_dropcount;
- }
-
- helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
- GFP_KERNEL);
- if (!helper_argv) {
- coredump_report_failure("%s failed to allocate memory", __func__);
- goto fail_dropcount;
- }
- for (argi = 0; argi < argc; argi++)
- helper_argv[argi] = cn.corename + argv[argi];
- helper_argv[argi] = NULL;
-
- retval = -ENOMEM;
- sub_info = call_usermodehelper_setup(helper_argv[0],
- helper_argv, NULL, GFP_KERNEL,
- umh_coredump_setup, NULL, &cprm);
- if (sub_info)
- retval = call_usermodehelper_exec(sub_info,
- UMH_WAIT_EXEC);
-
- kfree(helper_argv);
- if (retval) {
- coredump_report_failure("|%s pipe failed", cn.corename);
- goto close_fail;
- }
- } else if (cn.core_type == COREDUMP_FILE) {
+ switch (cn.core_type) {
+ case COREDUMP_FILE: {
struct mnt_idmap *idmap;
struct inode *inode;
int open_flags = O_CREAT | O_WRONLY | O_NOFOLLOW |
@@ -796,6 +741,69 @@ void do_coredump(const kernel_siginfo_t *siginfo)
if (do_truncate(idmap, cprm.file->f_path.dentry,
0, 0, cprm.file))
goto close_fail;
+ break;
+ }
+ case COREDUMP_PIPE: {
+ int argi;
+ int dump_count;
+ char **helper_argv;
+ struct subprocess_info *sub_info;
+
+ if (cprm.limit == 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
+ * cprm.limit of 1 here as a special value, this is a
+ * consistent way to catch recursive crashes.
+ * We can still crash if the core_pattern binary sets
+ * RLIM_CORE = !1, but it runs as root, and can do
+ * lots of stupid things.
+ *
+ * Note that we use task_tgid_vnr here to grab the pid
+ * of the process group leader. That way we get the
+ * right pid if a thread in a multi-threaded
+ * core_pattern process dies.
+ */
+ coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
+ goto fail_unlock;
+ }
+ cprm.limit = RLIM_INFINITY;
+
+ dump_count = atomic_inc_return(&core_dump_count);
+ if (core_pipe_limit && (core_pipe_limit < dump_count)) {
+ coredump_report_failure("over core_pipe_limit, skipping core dump");
+ goto fail_dropcount;
+ }
+
+ helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
+ GFP_KERNEL);
+ if (!helper_argv) {
+ coredump_report_failure("%s failed to allocate memory", __func__);
+ goto fail_dropcount;
+ }
+ for (argi = 0; argi < argc; argi++)
+ helper_argv[argi] = cn.corename + argv[argi];
+ helper_argv[argi] = NULL;
+
+ retval = -ENOMEM;
+ sub_info = call_usermodehelper_setup(helper_argv[0],
+ helper_argv, NULL, GFP_KERNEL,
+ umh_coredump_setup, NULL, &cprm);
+ if (sub_info)
+ retval = call_usermodehelper_exec(sub_info,
+ UMH_WAIT_EXEC);
+
+ kfree(helper_argv);
+ if (retval) {
+ coredump_report_failure("|%s pipe failed", cn.corename);
+ goto close_fail;
+ }
+ break;
+ }
+ default:
+ WARN_ON_ONCE(true);
+ goto close_fail;
}

/* get us an unshared descriptor table; almost always a no-op */

--
2.47.2