A process can disable access to the alternate signal stack and still expect signals to be delivered correctly. get_sigframe() updates the PKRU value to enable access to the altstack, and makes sure that the value on the sigframe is the user-defined PKRU value so that it is correctly restored. However, in sigreturn(), restore_altstack() needs read access to the altstack. But the PKRU has already been restored from the sigframe (in restore_sigcontext()) which will disable access to the altstack, resulting in a SIGSEGV. Fix this by restoring altstack before restoring PKRU. Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@xxxxxxxxxx> --- arch/x86/kernel/signal_64.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c index 8a94053c5444..ee9453891901 100644 --- a/arch/x86/kernel/signal_64.c +++ b/arch/x86/kernel/signal_64.c @@ -260,13 +260,13 @@ SYSCALL_DEFINE0(rt_sigreturn) set_current_blocked(&set); - if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) + if (restore_altstack(&frame->uc.uc_stack)) goto badframe; - if (restore_signal_shadow_stack()) + if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) goto badframe; - if (restore_altstack(&frame->uc.uc_stack)) + if (restore_signal_shadow_stack()) goto badframe; return regs->ax; -- 2.39.3
