From cf92738fa5dee24050028a1235f815f2a0fd33b5 Mon Sep 17 00:00:00 2001 From: Dmitriy Ivanov Date: Wed, 14 Oct 2015 11:15:45 -0700 Subject: [PATCH] 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 --- linker/linker.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/linker/linker.cpp b/linker/linker.cpp index c99042ff1..d3ac1d000 100644 --- a/linker/linker.cpp +++ b/linker/linker.cpp @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -317,6 +318,13 @@ static void parse_LD_PRELOAD(const char* path) { static bool realpath_fd(int fd, std::string* realpath) { std::vector 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; -- 2.11.0