[PATCH 07/20] signal/powerpc: On swapcontext failure force SIGSEGV

Eric W. Biederman
2021-10-20T17:45:02Z

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 <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@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")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/powerpc/kernel/signal_32.c | 6 ++++--
arch/powerpc/kernel/signal_64.c | 9 ++++++---
2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 0608581967f0..666f3da41232 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -1062,8 +1062,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
* 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;
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..d8de622c9e4a 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -703,15 +703,18 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
* 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();

--
2.20.1