Merge branch 'fix/avoid-large-stack-buffers' of https://github.com/dtzWill/nix

3 files changed, 21 insertions, 20 deletions

diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index a1d9d3233a..b2459336a8 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -40,14 +40,14 @@ static void dumpContents(const Path & path, size_t size,
     AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
     if (!fd) throw SysError(format("opening file '%1%'") % path);
 
-    unsigned char buf[65536];
+    std::vector<unsigned char> buf(65536);
     size_t left = size;
 
     while (left > 0) {
-        size_t n = left > sizeof(buf) ? sizeof(buf) : left;
-        readFull(fd.get(), buf, n);
+        size_t n = left > buf.size() ? buf.size() : left;
+        readFull(fd.get(), buf.data(), n);
         left -= n;
-        sink(buf, n);
+        sink(buf.data(), n);
     }
 
     writePadding(size, sink);
@@ -146,14 +146,14 @@ static void parseContents(ParseSink & sink, Source & source, const Path & path)
     sink.preallocateContents(size);
 
     unsigned long long left = size;
-    unsigned char buf[65536];
+    std::vector<unsigned char> buf(65536);
 
     while (left) {
         checkInterrupt();
-        unsigned int n = sizeof(buf);
-        if ((unsigned long long) n > left) n = left;
-        source(buf, n);
-        sink.receiveContents(buf, n);
+        auto n = buf.size();
+        if ((unsigned long long)n > left) n = left;
+        source(buf.data(), n);
+        sink.receiveContents(buf.data(), n);
         left -= n;
     }
 
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index 150995f55f..a01d651e1e 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -257,12 +257,12 @@ Hash hashFile(HashType ht, const Path & path)
     AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
     if (!fd) throw SysError(format("opening file '%1%'") % path);
 
-    unsigned char buf[8192];
+    std::vector<unsigned char> buf(8192);
     ssize_t n;
-    while ((n = read(fd.get(), buf, sizeof(buf)))) {
+    while ((n = read(fd.get(), buf.data(), buf.size()))) {
         checkInterrupt();
         if (n == -1) throw SysError(format("reading file '%1%'") % path);
-        update(ht, ctx, buf, n);
+        update(ht, ctx, buf.data(), n);
     }
 
     finish(ht, ctx, hash.hash);
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index ab2d097f8b..15962236ec 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -230,16 +230,17 @@ bool pathExists(const Path & path)
 Path readLink(const Path & path)
 {
     checkInterrupt();
+    std::vector<char> buf;
     for (ssize_t bufSize = PATH_MAX/4; true; bufSize += bufSize/2) {
-        char buf[bufSize];
-        ssize_t rlSize = readlink(path.c_str(), buf, bufSize);
+        buf.resize(bufSize);
+        ssize_t rlSize = readlink(path.c_str(), buf.data(), bufSize);
         if (rlSize == -1)
             if (errno == EINVAL)
                 throw Error("'%1%' is not a symlink", path);
             else
                 throw SysError("reading symbolic link '%1%'", path);
         else if (rlSize < bufSize)
-            return string(buf, rlSize);
+            return string(buf.data(), rlSize);
     }
 }
 
@@ -294,10 +295,10 @@ string readFile(int fd)
     if (fstat(fd, &st) == -1)
         throw SysError("statting file");
 
-    auto buf = std::make_unique<unsigned char[]>(st.st_size);
-    readFull(fd, buf.get(), st.st_size);
+    std::vector<unsigned char> buf(st.st_size);
+    readFull(fd, buf.data(), st.st_size);
 
-    return string((char *) buf.get(), st.st_size);
+    return string((char *) buf.data(), st.st_size);
 }
 
 
@@ -439,10 +440,10 @@ Path createTempDir(const Path & tmpRoot, const Path & prefix,
 static Lazy<Path> getHome2([]() {
     Path homeDir = getEnv("HOME");
     if (homeDir.empty()) {
-        char buf[16384];
+        std::vector<char> buf(16384);
         struct passwd pwbuf;
         struct passwd * pw;
-        if (getpwuid_r(getuid(), &pwbuf, buf, sizeof(buf), &pw) != 0
+        if (getpwuid_r(getuid(), &pwbuf, buf.data(), buf.size(), &pw) != 0
             || !pw || !pw->pw_dir || !pw->pw_dir[0])
             throw Error("cannot determine user's home directory");
         homeDir = pw->pw_dir;