Re: [PATCH 09/10] pidfs: record the coredump on the dumping thread's pid too
From: Alexander Mikhalitsyn <hidden>
Date: 2026-09-07 10:59:25
Also in:
linux-fsdevel, lkml
Am Mo., 31. Aug. 2026 um 13:22 Uhr schrieb Christian Brauner [off-list ref]:
If a thread-group coredumps only the thread-group leader pidfd will return coredump information. A pidfd for the thread that took the fatal signal cannot be used to retrieve it. Record both the thread-group leader and the specific thread that took the signal and register both in pidfs. Mark both the thread-group leader and the specific thread with the coredump information so retrieval works for both pidfds. Now that both SO_PEERPIDFD and SO_PEERPIDFD_THREAD are available it's easy to get the coredump information for the specific thread. Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
LGTM Reviewed-by: Alexander Mikhalitsyn <redacted>
quoted hunk ↗ jump to hunk
--- fs/coredump.c | 22 +++++++++++++--------- fs/pidfs.c | 11 +++++++++-- include/linux/coredump.h | 4 +++- 3 files changed, 25 insertions(+), 12 deletions(-)diff --git a/fs/coredump.c b/fs/coredump.c index 71a0093ada1b..b5ff4b3e1831 100644 --- a/fs/coredump.c +++ b/fs/coredump.c@@ -454,7 +454,7 @@ static bool coredump_parse(struct core_name *cn, struct coredump_params *cprm, * leader we know that the thread-group leader * cannot be reaped until @current has exited. */ - cprm->pid = task_tgid(current); + task_pids(cprm->pid, current); err = cn_printf(cn, "%d", COREDUMP_PIDFD_NUMBER); break; }@@ -626,13 +626,17 @@ static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) struct coredump_params *cp = (struct coredump_params *)info->data; int err; - if (cp->pid) { + if (cp->pid[PIDTYPE_TGID]) { struct file *pidfs_file __free(fput) = NULL; - pidfs_file = pidfs_alloc_file(cp->pid, 0); + pidfs_file = pidfs_alloc_file(cp->pid[PIDTYPE_TGID], 0); if (IS_ERR(pidfs_file)) return PTR_ERR(pidfs_file); + err = pidfs_register_pids(cp->pid); + if (err) + return err; + pidfs_coredump(cp); /*@@ -695,12 +699,12 @@ static bool coredump_sock_connect(struct core_name *cn, struct coredump_params * return false; /* - * Set the thread-group leader pid which is used for the peer - * credentials during connect() below. Then immediately register - * it in pidfs... + * Set the pids of the dumping thread and its thread-group leader + * which are used for the peer credentials during connect() below. + * Then immediately register them in pidfs... */ - cprm->pid = task_tgid(current); - retval = pidfs_register_pid(cprm->pid); + task_pids(cprm->pid, current); + retval = pidfs_register_pids(cprm->pid); if (retval) return false;@@ -722,7 +726,7 @@ static bool coredump_sock_connect(struct core_name *cn, struct coredump_params * } /* ... and validate that @sk_peer_pid matches @cprm.pid. */ - if (WARN_ON_ONCE(unix_peer(socket->sk)->sk_peer_pid[PIDTYPE_TGID] != cprm->pid)) + if (WARN_ON_ONCE(!pids_equal(unix_peer(socket->sk)->sk_peer_pid, cprm->pid))) return false; cprm->limit = RLIM_INFINITY;diff --git a/fs/pidfs.c b/fs/pidfs.c index 586af2e5811c..29299b2c7ca7 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c@@ -793,9 +793,9 @@ void pidfs_exit(struct task_struct *tsk) } #ifdef CONFIG_COREDUMP -void pidfs_coredump(const struct coredump_params *cprm) +static void pidfs_coredump_pid(struct pid *pid, + const struct coredump_params *cprm) { - struct pid *pid = cprm->pid; struct pidfs_attr *attr; attr = READ_ONCE(pid->attr);@@ -814,6 +814,13 @@ void pidfs_coredump(const struct coredump_params *cprm) smp_wmb(); set_bit(PIDFS_ATTR_BIT_COREDUMP, &attr->attr_mask); } + +void pidfs_coredump(const struct coredump_params *cprm) +{ + /* The dumping thread's pidfd reports the coredump as well. */ + for (enum pid_type type = PIDTYPE_PID; type <= pids_last(cprm->pid); type++) + pidfs_coredump_pid(cprm->pid[type], cprm); +} #endif static struct vfsmount *pidfs_mnt __ro_after_init;diff --git a/include/linux/coredump.h b/include/linux/coredump.h index 7b38ee2e7913..0bbb7de6a402 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h@@ -5,6 +5,7 @@ #include <linux/types.h> #include <linux/mm.h> #include <linux/fs.h> +#include <linux/pid_types.h> #include <linux/sched/coredump.h> #include <asm/siginfo.h>@@ -32,7 +33,8 @@ struct coredump_params { int vma_count; size_t vma_data_size; struct core_vma_metadata *vma_meta; - struct pid *pid; + /* Dumping thread and its thread-group leader by pid type. */ + DECLARE_PIDS(pid, PIDTYPE_TGID); }; extern unsigned int core_file_note_size_limit; --2.53.0