Patch "signal/powerpc: On swapcontext failure force SIGSEGV" has been added to the 5.15-stable tree

This is a note to let you know that I've just added the patch titled

signal/powerpc: On swapcontext failure force SIGSEGV

to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
signal-powerpc-on-swapcontext-failure-force-sigsegv.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 83a1f27ad773b1d8f0460d3a676114c7651918cc Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <[email protected]>
Date: Wed, 20 Oct 2021 12:43:53 -0500
Subject: signal/powerpc: On swapcontext failure force SIGSEGV

From: Eric W. Biederman <[email protected]>

commit 83a1f27ad773b1d8f0460d3a676114c7651918cc upstream.

If the register state may be partial and corrupted instead of calling do_exit, call force_sigsegv(SIGSEGV). Which properly kills the process with SIGSEGV and does not let any more userspace code execute, instead of just killing one thread of the process and potentially confusing everything.

Cc: Michael Ellerman <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: [email protected]
History-tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git

---
 arch/powerpc/kernel/signal_32.c |    6 ++++--
 arch/powerpc/kernel/signal_64.c |    9 ++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

@@ -1062,8 +1062,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucon
 	 * or if another thread unmaps the region containing the context.
 	 * We kill the task with a SIGSEGV in this situation.
 	 */
-	if (do_setcontext(new_ctx, regs, 0))
-		do_exit(SIGSEGV);
+	if (do_setcontext(new_ctx, regs, 0)) {
+		force_sigsegv(SIGSEGV);
+		return -EFAULT;
+	}
 
 	set_thread_flag(TIF_RESTOREALL);
 	return 0;

@@ -703,15 +703,18 @@ SYSCALL_DEFINE3(swapcontext, struct ucon
 	 * We kill the task with a SIGSEGV in this situation.
 	 */
 
-	if (__get_user_sigset(&set, &new_ctx->uc_sigmask))
-		do_exit(SIGSEGV);
+	if (__get_user_sigset(&set, &new_ctx->uc_sigmask)) {
+		force_sigsegv(SIGSEGV);
+		return -EFAULT;
+	}
 	set_current_blocked(&set);
 
 	if (!user_read_access_begin(new_ctx, ctx_size))
 		return -EFAULT;
 	if (__unsafe_restore_sigcontext(current, NULL, 0, &new_ctx->uc_mcontext)) {
 		user_read_access_end();
-		do_exit(SIGSEGV);
+		force_sigsegv(SIGSEGV);
+		return -EFAULT;
 	}
 	user_read_access_end();
 

Patches currently in stable-queue which might be from [email protected] are

queue-5.15/signal-vm86_32-properly-send-sigsegv-when-the-vm86-state-cannot-be-saved.patch queue-5.15/signal-don-t-always-set-sa_immutable-for-forced-signals.patch queue-5.15/signal-x86-in-emulate_vsyscall-force-a-signal-instead-of-calling-do_exit.patch queue-5.15/ipc-warn-if-trying-to-remove-ipc-object-which-is-absent.patch queue-5.15/signal-replace-force_sigsegv-sigsegv-with-force_fatal_sig-sigsegv.patch queue-5.15/signal-powerpc-on-swapcontext-failure-force-sigsegv.patch queue-5.15/exit-syscall_user_dispatch-send-ordinary-signals-on-failure.patch queue-5.15/signal-s390-use-force_sigsegv-in-default_trap_handler.patch queue-5.15/signal-implement-force_fatal_sig.patch queue-5.15/signal-sparc32-in-setup_rt_frame-and-setup_fram-use-force_fatal_sig.patch queue-5.15/signal-sparc32-exit-with-a-fatal-signal-when-try_to_clear_window_buffer-fails.patch queue-5.15/shm-extend-forced-shm-destroy-to-support-objects-from-several-ipc-nses.patch queue-5.15/signal-replace-force_fatal_sig-with-force_exit_sig-when-in-doubt.patch