From 784e0300fe9fe4aa81bd7df9d59e138f56bb605b Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 22 Jun 2018 11:45:07 +0100 Subject: 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 Signed-off-by: Thomas Gleixner Acked-by: Mathieu Desnoyers 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 --- arch/arm/kernel/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/arm/kernel') 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) * Increment event counter and perform fixup for the pre-signal * frame. */ - rseq_signal_deliver(regs); + rseq_signal_deliver(ksig, regs); /* * Set up the stack frame @@ -666,7 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) } else { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); - rseq_handle_notify_resume(regs); + rseq_handle_notify_resume(NULL, regs); } } local_irq_disable(); -- cgit v1.2.3 From cea394772d3c41d04cb71a032f6ed878392bd134 Mon Sep 17 00:00:00 2001 From: Vladimir Murzin Date: Mon, 18 Jun 2018 14:33:03 +0100 Subject: ARM: 8775/1: NOMMU: Use instr_sync instead of plain isb in common code Greg reported that commit 3c24121039c9d ("ARM: 8756/1: NOMMU: Postpone MPU activation till __after_proc_init") is causing breakage for the old Versatile platform in no-MMU mode (with out-of-tree patches): AS arch/arm/kernel/head-nommu.o arch/arm/kernel/head-nommu.S: Assembler messages: arch/arm/kernel/head-nommu.S:180: Error: selected processor does not support `isb' in ARM mode scripts/Makefile.build:417: recipe for target 'arch/arm/kernel/head-nommu.o' failed make[2]: *** [arch/arm/kernel/head-nommu.o] Error 1 Makefile:1034: recipe for target 'arch/arm/kernel' failed make[1]: *** [arch/arm/kernel] Error 2 Since the code is common for all NOMMU builds usage of the isb was a bad idea (please, note that isb also used in MPU related code which is fine because MPU has dependency on CPU_V7/CPU_V7M), instead use more robust instr_sync assembler macro. Fixes: 3c24121039c9 ("ARM: 8756/1: NOMMU: Postpone MPU activation till __after_proc_init") Reported-by: Greg Ungerer Tested-by: Greg Ungerer Signed-off-by: Vladimir Murzin Signed-off-by: Russell King --- arch/arm/kernel/head-nommu.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arm/kernel') diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index dd546d65a383..7a9b86978ee1 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -177,7 +177,7 @@ M_CLASS(streq r3, [r12, #PMSAv8_MAIR1]) bic r0, r0, #CR_I #endif mcr p15, 0, r0, c1, c0, 0 @ write control reg - isb + instr_sync #elif defined (CONFIG_CPU_V7M) #ifdef CONFIG_ARM_MPU ldreq r3, [r12, MPU_CTRL] -- cgit v1.2.3