executor: set fixed fd for the extra coverage kcov instance

Currently it is dup2'd to 0, which is quite likely to be closed by the
fuzzer. Dup2 it to a safer fd instead.

1 files changed, 2 insertions, 0 deletions

diff --git a/executor/executor.cc b/executor/executor.cc
index b11faa684..e4034310d 100644
--- a/executor/executor.cc
+++ b/executor/executor.cc
@@ -71,6 +71,7 @@ const int kPreMmapCoverThreads = 3; // the number of kcov instances to mmap duri
 const int kInPipeFd = kMaxFd - 1; // remapped from stdin
 const int kOutPipeFd = kMaxFd - 2; // remapped from stdout
 const int kCoverFd = kOutPipeFd - kMaxThreads;
+const int kExtraCoverFd = kCoverFd - 1;
 const int kMaxArgs = 9;
 const int kCoverSize = 256 << 10;
 const int kFailStatus = 67;
@@ -477,6 +478,7 @@ int main(int argc, char** argv)
 				thread_mmap_cover(&threads[i]);
 			}
 		}
+		extra_cov.fd = kExtraCoverFd;
 		cover_open(&extra_cov, true);
 		cover_mmap(&extra_cov);
 		cover_protect(&extra_cov);