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Subject[PATCH 4/4] x86: SROP mitigation: implement signal counting

This patch implements signal counting for x86-64, x86-32 and x32.

Signed-off-by: Erik Bosman <erik@minemu.org>

---
arch/x86/Kconfig | 1 +
arch/x86/ia32/ia32_signal.c | 10 ++++++++++
arch/x86/kernel/signal.c | 19 +++++++++++++++++++
3 files changed, 30 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 83eea28..82d779f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -129,6 +129,7 @@ config X86
select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64
select HAVE_CC_STACKPROTECTOR
select HAVE_SIGNAL_CANARY
+ select HAVE_SIGNAL_BOOKKEEPING
select GENERIC_CPU_AUTOPROBE
select HAVE_ARCH_AUDITSYSCALL

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 1a9285a..5b95c26 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -219,6 +219,11 @@ asmlinkage long sys32_sigreturn(void)
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;

+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ if (signals_in_progress_dec(current))
+ goto badframe;
+#endif
+
#ifdef CONFIG_SIGNAL_CANARY
if (__get_user(canary, &frame->canary) || (canary != current->signal_canary))
goto badframe;
@@ -257,6 +262,11 @@ asmlinkage long sys32_rt_sigreturn(void)
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;

+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ if (signals_in_progress_dec(current))
+ goto badframe;
+#endif
+
#ifdef CONFIG_SIGNAL_CANARY
if (__get_user(canary, &frame->canary) || (canary != current->signal_canary))
goto badframe;
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 0cc4556..5f51e8c 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -558,6 +558,11 @@ asmlinkage unsigned long sys_sigreturn(void)
u32 canary;
#endif

+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ if (signals_in_progress_dec(current))
+ goto badframe;
+#endif
+
frame = (struct sigframe __user *)(regs->sp - 8);

if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -600,6 +605,11 @@ asmlinkage long sys_rt_sigreturn(void)
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;

+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ if (signals_in_progress_dec(current))
+ goto badframe;
+#endif
+
#ifdef CONFIG_SIGNAL_CANARY
if (__get_user(canary, &frame->canary) || (canary != current->signal_canary))
goto badframe;
@@ -708,6 +718,10 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
}
signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
+
+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ signals_in_progress_inc(current);
+#endif
}

#ifdef CONFIG_X86_32
@@ -824,6 +838,11 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
goto badframe;

+#ifdef CONFIG_SIGNAL_BOOKKEEPING
+ if (signals_in_progress_dec(current))
+ goto badframe;
+#endif
+
#ifdef CONFIG_SIGNAL_CANARY
if (__get_user(canary, &frame->canary) || (canary != current->signal_canary))
goto badframe;
--
1.9.1


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