Ensure that readlink has access to /proc/self/fd
/proc/self/fd is not available when PR_DUMPABLE is set to 0
which is default for the user builds. It leads to permission
denials on readlink.
This change fixes the problem by setting PR_DUMPABLE flag to 1
for readlink and restoring it's previous value after the call.
Bug: http://b/24912743
Change-Id: I3fd179c5c6b56af96d6a15ee597024ccb15e1a13
diff --git a/linker/linker.cpp b/linker/linker.cpp
index c99042f..d3ac1d0 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -37,6 +37,7 @@
#include <string.h>
#include <sys/mman.h>
#include <sys/param.h>
+#include <sys/prctl.h>
#include <unistd.h>
#include <new>
@@ -317,6 +318,13 @@
static bool realpath_fd(int fd, std::string* realpath) {
std::vector<char> buf(PATH_MAX), proc_self_fd(PATH_MAX);
snprintf(&proc_self_fd[0], proc_self_fd.size(), "/proc/self/fd/%d", fd);
+ // set DUMPABLE to 1 to access /proc/self/fd
+ int dumpable = prctl(PR_GET_DUMPABLE, 0, 0, 0, 0);
+ prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
+ auto guard = make_scope_guard([&]() {
+ // restore dumpable
+ prctl(PR_SET_DUMPABLE, dumpable, 0, 0, 0);
+ });
if (readlink(&proc_self_fd[0], &buf[0], buf.size()) == -1) {
PRINT("readlink('%s') failed: %s [fd=%d]", &proc_self_fd[0], strerror(errno), fd);
return false;
