[PATCH 5.15 258/279] signal/powerpc: On swapcontext failure force SIGSEGV

[Greg Kroah-Hartman]

From: Eric W. Biederman <ebied...@xmission.com>

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 <m...@ellerman.id.au>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
History-tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Fixes: 756f1ae8a44e ("PPC32: Rework signal code and add a swapcontext system 
call.")
Fixes: 04879b04bf50 ("[PATCH] ppc64: VMX (Altivec) support & signal32 rework, 
from Ben Herrenschmidt")
Link: https://lkml.kernel.org/r/20211020174406.17889-7-ebied...@xmission.com
Signed-off-by: Eric W. Biederman <ebied...@xmission.com>
Cc: Thomas Backlund <t...@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 arch/powerpc/kernel/signal_32.c |    6 ++++--
 arch/powerpc/kernel/signal_64.c |    9 ++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -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;
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -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();