5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner commit c0e659511d4f49087da095a95799edb5b775a705 upstream. If the calling thread has blocked a signal then retarget_shared_pending() slingshots a shared pending signal to a sibling thread. Today it only skips PF_EXITING threads but not a coredumping thread. But if SIGNAL_GROUP_EXIT is set no thread in the thread-group can dequeue such signals anymore as get_signal() sends SIGKILL to every thread and prepare_signal() drops any other signal. exit_signals() also returns early on SIGNAL_GROUP_EXIT. But neither sigprocmask() nor the mask restore in sigtimedwait() do. Say a thread sleeps in sigtimedwait() and a sibling thread crashes. The sleeping thread gets woken by the zap call. It restores its mask on the way out and retargets a signal that was queued for the coredumping process. That means TIF_SIGPENDING is set on the coredumping task which zap_threads() had cleared. So a blocking write sees TIF_SIGPENDING and truncates the dump. Stop retargeting signals when SIGNAL_GROUP_EXIT is set and avoid needlessly truncating coredumps. Fixes: e6fa16ab9c1e ("signal: sigprocmask() should do retarget_shared_pending()") Cc: stable@vger.kernel.org Acked-by: Oleg Nesterov Link: https://patch.msgid.link/20260921-work-coredump-fixes-v3-5-8e4adb1619e6@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2830,6 +2830,10 @@ static void retarget_shared_pending(stru sigset_t retarget; struct task_struct *t; + /* Nobody dequeues them in a dying group, see get_signal(). */ + if (tsk->signal->flags & SIGNAL_GROUP_EXIT) + return; + sigandsets(&retarget, &tsk->signal->shared_pending.signal, which); if (sigisemptyset(&retarget)) return;