From 9b5da65034da5489edcd0c12330bbf3faf032d71 Mon Sep 17 00:00:00 2001
From: Jian Cai <jiancai@google.com>
Date: Thu, 1 Apr 2021 11:37:15 -0700
Subject: [PATCH] libsandbox: retry ptrace when PTRACE_GETREGS is used.

Call ptrace again if it fails when the request type is PTRACE_GETREGS.

Signed-off-by: Jian Cai <jiancai@google.com>
---
 libsandbox/trace.c    | 12 +++++++++++-
 libsandbox/wrappers.h |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/libsandbox/trace.c b/libsandbox/trace.c
index 3efef23..c87c4eb 100644
--- a/libsandbox/trace.c
+++ b/libsandbox/trace.c
@@ -56,6 +56,7 @@ static void trace_exit(int status)
 static long _do_ptrace(sb_ptrace_req_t request, const char *srequest, void *addr, void *data)
 {
 	long ret;
+	bool retried = false;
  try_again:
 	errno = 0;
 	ret = ptrace(request, trace_pid, addr, data);
@@ -74,11 +75,20 @@ static long _do_ptrace(sb_ptrace_req_t request, const char *srequest, void *addr
 			 * That's not something the sandbox should abort on. #560396
 			 */
 			return ret;
-		} else if (!errno)
+		} else if (!errno) {
 			if (request == PTRACE_PEEKDATA ||
 			    request == PTRACE_PEEKTEXT ||
 			    request == PTRACE_PEEKUSER)
 				return ret;
+			// Retry once when PTRACE_GETREGS is used. #1188969
+			if (request == PTRACE_GETREGS) {
+				if (!retried && (random() % 10) != 0) {
+					retried = true;
+					goto try_again;
+				}
+				sb_unwrapped_system("(set -x; uname -a; ps af -o pgid,ppid,pid,etime,cputime,%cpu,command; dmesg | tail -n100;) >/dev/tty 2>&1");
+			}
+		}
 
 		sb_ebort("ISE:_do_ptrace: ptrace(%s, ..., %p, %p): %s\n",
 			srequest, addr, data, strerror(errno));
diff --git a/libsandbox/wrappers.h b/libsandbox/wrappers.h
index bf5bf64..5f4ac2a 100644
--- a/libsandbox/wrappers.h
+++ b/libsandbox/wrappers.h
@@ -21,6 +21,8 @@ attribute_hidden char *sb_unwrapped_getcwd (char *, size_t);
 attribute_hidden int   sb_unwrapped_open   (const char *, int, mode_t);
 #define                sb_unwrapped_popen  sb_unwrapped_popen_DEFAULT
 attribute_hidden FILE *sb_unwrapped_popen  (const char *, const char *);
+#define                sb_unwrapped_system sb_unwrapped_system_DEFAULT
+attribute_hidden int   sb_unwrapped_system  (const char *);
 
 attribute_hidden bool sb_fopen_pre_check    (const char *func, const char *pathname, const char *mode);
 attribute_hidden bool sb_fopen64_pre_check  (const char *func, const char *pathname, const char *mode);
-- 
2.31.1.498.g6c1eba8ee3d-goog