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authorWill Deacon <will.deacon@arm.com>2018-06-22 06:45:07 -0400
committerThomas Gleixner <tglx@linutronix.de>2018-06-22 13:04:22 -0400
commit784e0300fe9fe4aa81bd7df9d59e138f56bb605b (patch)
tree442642dae3c8e1b50ab68460c2e7662684d9e194
parent9a789fcfe8605417f7a1a970355f5efa4fe88c64 (diff)
rseq: Avoid infinite recursion when delivering SIGSEGV
When delivering a signal to a task that is using rseq, we call into __rseq_handle_notify_resume() so that the registers pushed in the sigframe are updated to reflect the state of the restartable sequence (for example, ensuring that the signal returns to the abort handler if necessary). However, if the rseq management fails due to an unrecoverable fault when accessing userspace or certain combinations of RSEQ_CS_* flags, then we will attempt to deliver a SIGSEGV. This has the potential for infinite recursion if the rseq code continuously fails on signal delivery. Avoid this problem by using force_sigsegv() instead of force_sig(), which is explicitly designed to reset the SEGV handler to SIG_DFL in the case of a recursive fault. In doing so, remove rseq_signal_deliver() from the internal rseq API and have an optional struct ksignal * parameter to rseq_handle_notify_resume() instead. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: peterz@infradead.org Cc: paulmck@linux.vnet.ibm.com Cc: boqun.feng@gmail.com Link: https://lkml.kernel.org/r/1529664307-983-1-git-send-email-will.deacon@arm.com
-rw-r--r--arch/arm/kernel/signal.c4
-rw-r--r--arch/powerpc/kernel/signal.c4
-rw-r--r--arch/x86/entry/common.c2
-rw-r--r--arch/x86/kernel/signal.c2
-rw-r--r--include/linux/sched.h18
-rw-r--r--kernel/rseq.c7
6 files changed, 21 insertions, 16 deletions
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index f09e9d66d605..dec130e7078c 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -544,7 +544,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
544 * Increment event counter and perform fixup for the pre-signal 544 * Increment event counter and perform fixup for the pre-signal
545 * frame. 545 * frame.
546 */ 546 */
547 rseq_signal_deliver(regs); 547 rseq_signal_deliver(ksig, regs);
548 548
549 /* 549 /*
550 * Set up the stack frame 550 * Set up the stack frame
@@ -666,7 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
666 } else { 666 } else {
667 clear_thread_flag(TIF_NOTIFY_RESUME); 667 clear_thread_flag(TIF_NOTIFY_RESUME);
668 tracehook_notify_resume(regs); 668 tracehook_notify_resume(regs);
669 rseq_handle_notify_resume(regs); 669 rseq_handle_notify_resume(NULL, regs);
670 } 670 }
671 } 671 }
672 local_irq_disable(); 672 local_irq_disable();
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 17fe4339ba59..b3e8db376ecd 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -134,7 +134,7 @@ static void do_signal(struct task_struct *tsk)
134 /* Re-enable the breakpoints for the signal stack */ 134 /* Re-enable the breakpoints for the signal stack */
135 thread_change_pc(tsk, tsk->thread.regs); 135 thread_change_pc(tsk, tsk->thread.regs);
136 136
137 rseq_signal_deliver(tsk->thread.regs); 137 rseq_signal_deliver(&ksig, tsk->thread.regs);
138 138
139 if (is32) { 139 if (is32) {
140 if (ksig.ka.sa.sa_flags & SA_SIGINFO) 140 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
@@ -170,7 +170,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
170 if (thread_info_flags & _TIF_NOTIFY_RESUME) { 170 if (thread_info_flags & _TIF_NOTIFY_RESUME) {
171 clear_thread_flag(TIF_NOTIFY_RESUME); 171 clear_thread_flag(TIF_NOTIFY_RESUME);
172 tracehook_notify_resume(regs); 172 tracehook_notify_resume(regs);
173 rseq_handle_notify_resume(regs); 173 rseq_handle_notify_resume(NULL, regs);
174 } 174 }
175 175
176 user_enter(); 176 user_enter();
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 92190879b228..3b2490b81918 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -164,7 +164,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
164 if (cached_flags & _TIF_NOTIFY_RESUME) { 164 if (cached_flags & _TIF_NOTIFY_RESUME) {
165 clear_thread_flag(TIF_NOTIFY_RESUME); 165 clear_thread_flag(TIF_NOTIFY_RESUME);
166 tracehook_notify_resume(regs); 166 tracehook_notify_resume(regs);
167 rseq_handle_notify_resume(regs); 167 rseq_handle_notify_resume(NULL, regs);
168 } 168 }
169 169
170 if (cached_flags & _TIF_USER_RETURN_NOTIFY) 170 if (cached_flags & _TIF_USER_RETURN_NOTIFY)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 445ca11ff863..92a3b312a53c 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -692,7 +692,7 @@ setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
692 * Increment event counter and perform fixup for the pre-signal 692 * Increment event counter and perform fixup for the pre-signal
693 * frame. 693 * frame.
694 */ 694 */
695 rseq_signal_deliver(regs); 695 rseq_signal_deliver(ksig, regs);
696 696
697 /* Set up the stack frame */ 697 /* Set up the stack frame */
698 if (is_ia32_frame(ksig)) { 698 if (is_ia32_frame(ksig)) {
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c1882643d455..9256118bd40c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1799,20 +1799,22 @@ static inline void rseq_set_notify_resume(struct task_struct *t)
1799 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); 1799 set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
1800} 1800}
1801 1801
1802void __rseq_handle_notify_resume(struct pt_regs *regs); 1802void __rseq_handle_notify_resume(struct ksignal *sig, struct pt_regs *regs);
1803 1803
1804static inline void rseq_handle_notify_resume(struct pt_regs *regs) 1804static inline void rseq_handle_notify_resume(struct ksignal *ksig,
1805 struct pt_regs *regs)
1805{ 1806{
1806 if (current->rseq) 1807 if (current->rseq)
1807 __rseq_handle_notify_resume(regs); 1808 __rseq_handle_notify_resume(ksig, regs);
1808} 1809}
1809 1810
1810static inline void rseq_signal_deliver(struct pt_regs *regs) 1811static inline void rseq_signal_deliver(struct ksignal *ksig,
1812 struct pt_regs *regs)
1811{ 1813{
1812 preempt_disable(); 1814 preempt_disable();
1813 __set_bit(RSEQ_EVENT_SIGNAL_BIT, &current->rseq_event_mask); 1815 __set_bit(RSEQ_EVENT_SIGNAL_BIT, &current->rseq_event_mask);
1814 preempt_enable(); 1816 preempt_enable();
1815 rseq_handle_notify_resume(regs); 1817 rseq_handle_notify_resume(ksig, regs);
1816} 1818}
1817 1819
1818/* rseq_preempt() requires preemption to be disabled. */ 1820/* rseq_preempt() requires preemption to be disabled. */
@@ -1861,10 +1863,12 @@ static inline void rseq_execve(struct task_struct *t)
1861static inline void rseq_set_notify_resume(struct task_struct *t) 1863static inline void rseq_set_notify_resume(struct task_struct *t)
1862{ 1864{
1863} 1865}
1864static inline void rseq_handle_notify_resume(struct pt_regs *regs) 1866static inline void rseq_handle_notify_resume(struct ksignal *ksig,
1867 struct pt_regs *regs)
1865{ 1868{
1866} 1869}
1867static inline void rseq_signal_deliver(struct pt_regs *regs) 1870static inline void rseq_signal_deliver(struct ksignal *ksig,
1871 struct pt_regs *regs)
1868{ 1872{
1869} 1873}
1870static inline void rseq_preempt(struct task_struct *t) 1874static inline void rseq_preempt(struct task_struct *t)
diff --git a/kernel/rseq.c b/kernel/rseq.c
index ae306f90c514..22b6acf1ad63 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -251,10 +251,10 @@ static int rseq_ip_fixup(struct pt_regs *regs)
251 * respect to other threads scheduled on the same CPU, and with respect 251 * respect to other threads scheduled on the same CPU, and with respect
252 * to signal handlers. 252 * to signal handlers.
253 */ 253 */
254void __rseq_handle_notify_resume(struct pt_regs *regs) 254void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs)
255{ 255{
256 struct task_struct *t = current; 256 struct task_struct *t = current;
257 int ret; 257 int ret, sig;
258 258
259 if (unlikely(t->flags & PF_EXITING)) 259 if (unlikely(t->flags & PF_EXITING))
260 return; 260 return;
@@ -268,7 +268,8 @@ void __rseq_handle_notify_resume(struct pt_regs *regs)
268 return; 268 return;
269 269
270error: 270error:
271 force_sig(SIGSEGV, t); 271 sig = ksig ? ksig->sig : 0;
272 force_sigsegv(sig, t);
272} 273}
273 274
274#ifdef CONFIG_DEBUG_RSEQ 275#ifdef CONFIG_DEBUG_RSEQ