From c7544894fe8de4f00c396c6fe4ce5c0542689bb5 Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@gmail.com>
Date: Fri, 1 Jan 2021 01:21:44 +0300
Subject: [PATCH] dump/ppc64,arm,mips: sanitize the ERESTART_RESTARTBLOCK ->
 EINTR transition

1. The -ERESTART_RESTARTBLOCK case in get_task_regs() depends on kernel
   internals too much, and for no reason. We shouldn't rely on fact that
   a) we are going to do sigreturn() and b) restore_sigcontext() always
   sets restart_block->fn = do_no_restart_syscall which returns -EINTR.

   Just change this code to enforce -EINTR after restore, this is what
   we actually want until we teach criu to handle ERESTART_RESTARTBLOCK.

2. Add pr_warn() to make the potential bug-reports more understandable,
   a sane application should handle -EINTR correctly but this is not
   always the case.

Fixes: #1325
Report-by: Mr Travis
Inspired-by: dd71cca58ada ("dump/x86: sanitize the ERESTART_RESTARTBLOCK -> EINTR transition")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
 compel/arch/arm/src/lib/infect.c   | 6 ++++--
 compel/arch/mips/src/lib/infect.c  | 7 ++++---
 compel/arch/ppc64/src/lib/infect.c | 4 ++--
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/compel/arch/arm/src/lib/infect.c b/compel/arch/arm/src/lib/infect.c
index 0053bef58..75b985b74 100644
--- a/compel/arch/arm/src/lib/infect.c
+++ b/compel/arch/arm/src/lib/infect.c
@@ -4,6 +4,8 @@
 #include <string.h>
 #include <compel/plugins/std/syscall-codes.h>
 #include <compel/asm/processor-flags.h>
+#include <errno.h>
+
 #include "common/page.h"
 #include "uapi/compel/asm/infect-types.h"
 #include "log.h"
@@ -91,8 +93,8 @@ int get_task_regs(pid_t pid, user_regs_struct_t *regs, save_regs_t save,
 			regs->ARM_pc -= 4;
 			break;
 		case -ERESTART_RESTARTBLOCK:
-			regs->ARM_r0 = __NR_restart_syscall;
-			regs->ARM_pc -= 4;
+			pr_warn("Will restore %d with interrupted system call\n", pid);
+			regs->ARM_r0 = -EINTR;
 			break;
 		}
 	}
diff --git a/compel/arch/mips/src/lib/infect.c b/compel/arch/mips/src/lib/infect.c
index 521528f76..35e947cc0 100755
--- a/compel/arch/mips/src/lib/infect.c
+++ b/compel/arch/mips/src/lib/infect.c
@@ -2,6 +2,8 @@
 #include <sys/uio.h>
 #include <sys/auxv.h>
 #include <sys/mman.h>
+#include <errno.h>
+
 #include <compel/asm/fpu.h>
 #include <compel/cpu.h>
 #include "errno.h"
@@ -142,9 +144,8 @@ int get_task_regs(pid_t pid, user_regs_struct_t *regs, save_regs_t save,
 		    regs->cp0_epc -= 4;
 		    break;
 		case ERESTART_RESTARTBLOCK:
-		    regs->regs[2] = __NR_restart_syscall;
-		    regs->regs[7] = regs->regs[26];
-		    regs->cp0_epc -= 4;
+		    pr_warn("Will restore %d with interrupted system call\n", pid);
+		    regs->regs[2] = -EINTR;
 		    break;
 	    }
 	    regs->regs[0] = 0;
diff --git a/compel/arch/ppc64/src/lib/infect.c b/compel/arch/ppc64/src/lib/infect.c
index 637acd46d..b2c725f62 100644
--- a/compel/arch/ppc64/src/lib/infect.c
+++ b/compel/arch/ppc64/src/lib/infect.c
@@ -330,8 +330,8 @@ static int __get_task_regs(pid_t pid, user_regs_struct_t *regs,
 			regs->nip -= 4;
 			break;
 		case ERESTART_RESTARTBLOCK:
-			regs->gpr[0] = __NR_restart_syscall;
-			regs->nip -= 4;
+			pr_warn("Will restore %d with interrupted system call\n", pid);
+			regs->gpr[3] = EINTR;
 			break;
 		}
 	}