coredump: massage do_coredump()

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

Link: https://lore.kernel.org/20250516-work-coredump-socket-v8-2-664f3caf2516@kernel.org
Acked-by: Luca Boccassi <luca.boccassi@gmail.com>
Reviewed-by: Jann Horn <jannh@google.com>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/coredump.c b/fs/coredump.c
index 45725465c29986e33a3da61c4d82d1a490522902..47c811d32028d959535de7df272cf42b39b8362e 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -643,63 +643,8 @@ 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 |
@@ -793,6 +738,69 @@ 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 */