[Sanitizer] Option to fallback to stderr if unable to open logfile (#158687)
Add the santizier option `log_fallback_to_stderr` which will set the
logpath to `stderr` if there is an error with the provided logpath.
We've seen this happen when process A has write permission to the
logpath, but process B does not. In this case, we'd like process B to
fallback to writing to `stderr`, rather than being killed.
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
index a2c0a9c..e8f219b 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_file.cpp
@@ -36,9 +36,17 @@
void ReportFile::ReopenIfNecessary() {
mu->CheckLocked();
- if (fd == kStdoutFd || fd == kStderrFd) return;
-
uptr pid = internal_getpid();
+ if (fallbackToStderrActive && fd_pid != pid) {
+ // If fallbackToStderrActive is set then we fellback to stderr. If this is a
+ // new process, mark fd as invalid so we attempt to open again.
+ CHECK_EQ(fd, kStderrFd);
+ fd = kInvalidFd;
+ fallbackToStderrActive = false;
+ }
+ if (fd == kStdoutFd || fd == kStderrFd)
+ return;
+
// If in tracer, use the parent's file.
if (pid == stoptheworld_tracer_pid)
pid = stoptheworld_tracer_ppid;
@@ -48,8 +56,7 @@
// process, close it now.
if (fd_pid == pid)
return;
- else
- CloseFile(fd);
+ CloseFile(fd);
}
const char *exe_name = GetProcessName();
@@ -65,18 +72,24 @@
error_t err;
fd = OpenFile(full_path, WrOnly, &err);
if (fd == kInvalidFd) {
- const char *ErrorMsgPrefix = "ERROR: Can't open file: ";
+ bool fallback = common_flags()->log_fallback_to_stderr;
+ const char *ErrorMsgPrefix =
+ fallback ? "WARNING: Can't open file, falling back to stderr: "
+ : "ERROR: Can't open file: ";
WriteToFile(kStderrFd, ErrorMsgPrefix, internal_strlen(ErrorMsgPrefix));
WriteToFile(kStderrFd, full_path, internal_strlen(full_path));
char errmsg[100];
internal_snprintf(errmsg, sizeof(errmsg), " (reason: %d)\n", err);
WriteToFile(kStderrFd, errmsg, internal_strlen(errmsg));
- Die();
+ if (!fallback)
+ Die();
+ fallbackToStderrActive = true;
+ fd = kStderrFd;
}
fd_pid = pid;
}
-static void RecursiveCreateParentDirs(char *path) {
+static void RecursiveCreateParentDirs(char *path, fd_t &fd) {
if (path[0] == '\0')
return;
for (int i = 1; path[i] != '\0'; ++i) {
@@ -85,12 +98,19 @@
continue;
path[i] = '\0';
if (!DirExists(path) && !CreateDir(path)) {
- const char *ErrorMsgPrefix = "ERROR: Can't create directory: ";
+ bool fallback = common_flags()->log_fallback_to_stderr;
+ const char *ErrorMsgPrefix =
+ fallback ? "WARNING: Can't create directory, falling back to stderr: "
+ : "ERROR: Can't create directory: ";
WriteToFile(kStderrFd, ErrorMsgPrefix, internal_strlen(ErrorMsgPrefix));
WriteToFile(kStderrFd, path, internal_strlen(path));
const char *ErrorMsgSuffix = "\n";
WriteToFile(kStderrFd, ErrorMsgSuffix, internal_strlen(ErrorMsgSuffix));
- Die();
+ if (!fallback)
+ Die();
+ path[i] = save;
+ fd = kStderrFd;
+ return;
}
path[i] = save;
}
@@ -164,12 +184,17 @@
if (path) {
uptr len = internal_strlen(path);
if (len > sizeof(path_prefix) - 100) {
- const char *message = "ERROR: Path is too long: ";
+ bool fallback = common_flags()->log_fallback_to_stderr;
+ const char *message =
+ fallback ? "WARNING: Path is too long, falling back to stderr: "
+ : "ERROR: Path is too long: ";
WriteToFile(kStderrFd, message, internal_strlen(message));
WriteToFile(kStderrFd, path, 8);
message = "...\n";
WriteToFile(kStderrFd, message, internal_strlen(message));
- Die();
+ if (!fallback)
+ Die();
+ path = "stderr";
}
}
@@ -183,7 +208,7 @@
fd = kStdoutFd;
} else {
ParseAndSetPath(path, path_prefix, kMaxPathLength);
- RecursiveCreateParentDirs(path_prefix);
+ RecursiveCreateParentDirs(path_prefix, fd);
}
}
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_file.h b/compiler-rt/lib/sanitizer_common/sanitizer_file.h
index bef2c84..b3a5fed 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_file.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_file.h
@@ -43,6 +43,9 @@
// PID of the process that opened fd. If a fork() occurs,
// the PID of child will be different from fd_pid.
uptr fd_pid;
+ // Set to true if the last attempt to open the logfile failed, perhaps due to
+ // permission errors
+ bool fallbackToStderrActive = false;
private:
void ReopenIfNecessary();
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc b/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
index c1e3530..650a458 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
@@ -65,6 +65,8 @@
bool, log_to_syslog, (bool)SANITIZER_ANDROID || (bool)SANITIZER_APPLE,
"Write all sanitizer output to syslog in addition to other means of "
"logging.")
+COMMON_FLAG(bool, log_fallback_to_stderr, false,
+ "When set, fallback to stderr if we are unable to open log path.")
COMMON_FLAG(
int, verbosity, 0,
"Verbosity level (0 - silent, 1 - a bit of output, 2+ - more output).")
diff --git a/compiler-rt/test/sanitizer_common/TestCases/Posix/sanitizer_set_report_path_fail.cpp b/compiler-rt/test/sanitizer_common/TestCases/Posix/sanitizer_set_report_path_fail.cpp
index af5187a..819678e 100644
--- a/compiler-rt/test/sanitizer_common/TestCases/Posix/sanitizer_set_report_path_fail.cpp
+++ b/compiler-rt/test/sanitizer_common/TestCases/Posix/sanitizer_set_report_path_fail.cpp
@@ -2,9 +2,11 @@
// Case 1: Try setting a path that is an invalid/inaccessible directory.
// RUN: not %run %t 2>&1 | FileCheck %s --check-prefix=ERROR1
+// RUN: %env_tool_opts=log_fallback_to_stderr=true %run %t 2>&1 | FileCheck %s --check-prefixes=ERROR1,FALLBACK
// Case 2: Try setting a path that is too large.
// RUN: not %run %t A 2>&1 | FileCheck %s --check-prefix=ERROR2
+// RUN: %env_tool_opts=log_fallback_to_stderr=true %run %t A 2>&1 | FileCheck %s --check-prefixes=ERROR2,FALLBACK
#include <sanitizer/common_interface_defs.h>
#include <stdio.h>
@@ -14,11 +16,12 @@
if (argc == 1) {
// Case 1
sprintf(buff, "%s/report", argv[0]);
- // ERROR1: Can't create directory: {{.*}}
+ // ERROR1: Can't create directory
} else {
// Case 2
snprintf(buff, sizeof(buff), "%04095d", 42);
- // ERROR2: Path is too long: 00000000...
+ // ERROR2: Path is too long
}
__sanitizer_set_report_path(buff);
}
+// FALLBACK: falling back to stderr
