diff --git a/otautil/include/otautil/rangeset.h b/otautil/include/otautil/rangeset.h
index c4234d1..af8ae2d 100644
--- a/otautil/include/otautil/rangeset.h
+++ b/otautil/include/otautil/rangeset.h
@@ -30,28 +30,35 @@
 
   explicit RangeSet(std::vector<Range>&& pairs);
 
+  // Parses the given string into a RangeSet. Returns the parsed RangeSet, or an empty RangeSet on
+  // errors.
   static RangeSet Parse(const std::string& range_text);
 
+  // Appends the given Range to the current RangeSet.
+  bool PushBack(Range range);
+
+  // Clears all the ranges from the RangeSet.
+  void Clear();
+
   std::string ToString() const;
 
-  // Get the block number for the i-th (starting from 0) block in the RangeSet.
+  // Gets the block number for the i-th (starting from 0) block in the RangeSet.
   size_t GetBlockNumber(size_t idx) const;
 
-  // RangeSet has half-closed half-open bounds. For example, "3,5" contains blocks 3 and 4. So "3,5"
-  // and "5,7" are not overlapped.
+  // Returns whether the current RangeSet overlaps with other. RangeSet has half-closed half-open
+  // bounds. For example, "3,5" contains blocks 3 and 4. So "3,5" and "5,7" are not overlapped.
   bool Overlaps(const RangeSet& other) const;
 
-  // size() gives the number of Range's in this RangeSet.
+  // Returns the number of Range's in this RangeSet.
   size_t size() const {
     return ranges_.size();
   }
 
-  // blocks() gives the number of all blocks in this RangeSet.
+  // Returns the total number of blocks in this RangeSet.
   size_t blocks() const {
     return blocks_;
   }
 
-  // We provide const iterators only.
   std::vector<Range>::const_iterator cbegin() const {
     return ranges_.cbegin();
   }
@@ -60,13 +67,20 @@
     return ranges_.cend();
   }
 
-  // Need to provide begin()/end() since range-based loop expects begin()/end().
+  std::vector<Range>::iterator begin() {
+    return ranges_.begin();
+  }
+
+  std::vector<Range>::iterator end() {
+    return ranges_.end();
+  }
+
   std::vector<Range>::const_iterator begin() const {
-    return ranges_.cbegin();
+    return ranges_.begin();
   }
 
   std::vector<Range>::const_iterator end() const {
-    return ranges_.cend();
+    return ranges_.end();
   }
 
   // Reverse const iterators for MoveRange().
@@ -78,6 +92,11 @@
     return ranges_.crend();
   }
 
+  // Returns whether the RangeSet is valid (i.e. non-empty).
+  explicit operator bool() const {
+    return !ranges_.empty();
+  }
+
   const Range& operator[](size_t i) const {
     return ranges_[i];
   }
@@ -109,6 +128,9 @@
 // every block in the original source.
 class SortedRangeSet : public RangeSet {
  public:
+  // The block size when working with offset and file length.
+  static constexpr size_t kBlockSize = 4096;
+
   SortedRangeSet() {}
 
   // Ranges in the the set should be mutually exclusive; and they're sorted by the start block.
@@ -122,8 +144,6 @@
   // Compute the block range the file occupies, and insert that range.
   void Insert(size_t start, size_t len);
 
-  void Clear();
-
   using RangeSet::Overlaps;
 
   bool Overlaps(size_t start, size_t len) const;
diff --git a/otautil/rangeset.cpp b/otautil/rangeset.cpp
index a121a4e..532cba4 100644
--- a/otautil/rangeset.cpp
+++ b/otautil/rangeset.cpp
@@ -16,8 +16,10 @@
 
 #include "otautil/rangeset.h"
 
+#include <limits.h>
 #include <stddef.h>
 
+#include <algorithm>
 #include <string>
 #include <utility>
 #include <vector>
@@ -28,47 +30,79 @@
 #include <android-base/strings.h>
 
 RangeSet::RangeSet(std::vector<Range>&& pairs) {
-  CHECK_NE(pairs.size(), static_cast<size_t>(0)) << "Invalid number of tokens";
-
-  // Sanity check the input.
-  size_t result = 0;
-  for (const auto& range : pairs) {
-    CHECK_LT(range.first, range.second) << "Empty or negative range: " << range.first << ", "
-                                        << range.second;
-    size_t sz = range.second - range.first;
-    CHECK_LE(result, SIZE_MAX - sz) << "RangeSet size overflow";
-    result += sz;
+  blocks_ = 0;
+  if (pairs.empty()) {
+    LOG(ERROR) << "Invalid number of tokens";
+    return;
   }
 
-  ranges_ = pairs;
-  blocks_ = result;
+  for (const auto& range : pairs) {
+    if (!PushBack(range)) {
+      Clear();
+      return;
+    }
+  }
 }
 
 RangeSet RangeSet::Parse(const std::string& range_text) {
   std::vector<std::string> pieces = android::base::Split(range_text, ",");
-  CHECK_GE(pieces.size(), static_cast<size_t>(3)) << "Invalid range text: " << range_text;
+  if (pieces.size() < 3) {
+    LOG(ERROR) << "Invalid range text: " << range_text;
+    return {};
+  }
 
   size_t num;
-  CHECK(android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX)))
-      << "Failed to parse the number of tokens: " << range_text;
-
-  CHECK_NE(num, static_cast<size_t>(0)) << "Invalid number of tokens: " << range_text;
-  CHECK_EQ(num % 2, static_cast<size_t>(0)) << "Number of tokens must be even: " << range_text;
-  CHECK_EQ(num, pieces.size() - 1) << "Mismatching number of tokens: " << range_text;
+  if (!android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX))) {
+    LOG(ERROR) << "Failed to parse the number of tokens: " << range_text;
+    return {};
+  }
+  if (num == 0) {
+    LOG(ERROR) << "Invalid number of tokens: " << range_text;
+    return {};
+  }
+  if (num % 2 != 0) {
+    LOG(ERROR) << "Number of tokens must be even: " << range_text;
+    return {};
+  }
+  if (num != pieces.size() - 1) {
+    LOG(ERROR) << "Mismatching number of tokens: " << range_text;
+    return {};
+  }
 
   std::vector<Range> pairs;
   for (size_t i = 0; i < num; i += 2) {
     size_t first;
-    CHECK(android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)));
     size_t second;
-    CHECK(android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX)));
-
+    if (!android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)) ||
+        !android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX))) {
+      return {};
+    }
     pairs.emplace_back(first, second);
   }
-
   return RangeSet(std::move(pairs));
 }
 
+bool RangeSet::PushBack(Range range) {
+  if (range.first >= range.second) {
+    LOG(ERROR) << "Empty or negative range: " << range.first << ", " << range.second;
+    return false;
+  }
+  size_t sz = range.second - range.first;
+  if (blocks_ >= SIZE_MAX - sz) {
+    LOG(ERROR) << "RangeSet size overflow";
+    return false;
+  }
+
+  ranges_.push_back(std::move(range));
+  blocks_ += sz;
+  return true;
+}
+
+void RangeSet::Clear() {
+  ranges_.clear();
+  blocks_ = 0;
+}
+
 std::string RangeSet::ToString() const {
   if (ranges_.empty()) {
     return "";
@@ -114,8 +148,6 @@
   return false;
 }
 
-static constexpr size_t kBlockSize = 4096;
-
 // Ranges in the the set should be mutually exclusive; and they're sorted by the start block.
 SortedRangeSet::SortedRangeSet(std::vector<Range>&& pairs) : RangeSet(std::move(pairs)) {
   std::sort(ranges_.begin(), ranges_.end());
@@ -158,11 +190,6 @@
   Insert(to_insert);
 }
 
-void SortedRangeSet::Clear() {
-  blocks_ = 0;
-  ranges_.clear();
-}
-
 bool SortedRangeSet::Overlaps(size_t start, size_t len) const {
   RangeSet rs({ { start / kBlockSize, (start + len - 1) / kBlockSize + 1 } });
   return Overlaps(rs);
diff --git a/tests/unit/rangeset_test.cpp b/tests/unit/rangeset_test.cpp
index b3ed992..5141bb6 100644
--- a/tests/unit/rangeset_test.cpp
+++ b/tests/unit/rangeset_test.cpp
@@ -17,12 +17,24 @@
 #include <signal.h>
 #include <sys/types.h>
 
+#include <limits>
 #include <vector>
 
 #include <gtest/gtest.h>
 
 #include "otautil/rangeset.h"
 
+TEST(RangeSetTest, ctor) {
+  RangeSet rs(std::vector<Range>{ Range{ 8, 10 }, Range{ 1, 5 } });
+  ASSERT_TRUE(rs);
+
+  RangeSet rs2(std::vector<Range>{});
+  ASSERT_FALSE(rs2);
+
+  RangeSet rs3(std::vector<Range>{ Range{ 8, 10 }, Range{ 5, 1 } });
+  ASSERT_FALSE(rs3);
+}
+
 TEST(RangeSetTest, Parse_smoke) {
   RangeSet rs = RangeSet::Parse("2,1,10");
   ASSERT_EQ(static_cast<size_t>(1), rs.size());
@@ -37,27 +49,64 @@
 
   // Leading zeros are fine. But android::base::ParseUint() doesn't like trailing zeros like "10 ".
   ASSERT_EQ(rs, RangeSet::Parse(" 2, 1,   10"));
-  ASSERT_EXIT(RangeSet::Parse("2,1,10 "), ::testing::KilledBySignal(SIGABRT), "");
+  ASSERT_FALSE(RangeSet::Parse("2,1,10 "));
 }
 
 TEST(RangeSetTest, Parse_InvalidCases) {
   // Insufficient number of tokens.
-  ASSERT_EXIT(RangeSet::Parse(""), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("2,1"), ::testing::KilledBySignal(SIGABRT), "");
+  ASSERT_FALSE(RangeSet::Parse(""));
+  ASSERT_FALSE(RangeSet::Parse("2,1"));
 
   // The first token (i.e. the number of following tokens) is invalid.
-  ASSERT_EXIT(RangeSet::Parse("a,1,1"), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("3,1,1"), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("-3,1,1"), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("2,1,2,3"), ::testing::KilledBySignal(SIGABRT), "");
+  ASSERT_FALSE(RangeSet::Parse("a,1,1"));
+  ASSERT_FALSE(RangeSet::Parse("3,1,1"));
+  ASSERT_FALSE(RangeSet::Parse("-3,1,1"));
+  ASSERT_FALSE(RangeSet::Parse("2,1,2,3"));
 
   // Invalid tokens.
-  ASSERT_EXIT(RangeSet::Parse("2,1,10a"), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("2,,10"), ::testing::KilledBySignal(SIGABRT), "");
+  ASSERT_FALSE(RangeSet::Parse("2,1,10a"));
+  ASSERT_FALSE(RangeSet::Parse("2,,10"));
 
   // Empty or negative range.
-  ASSERT_EXIT(RangeSet::Parse("2,2,2"), ::testing::KilledBySignal(SIGABRT), "");
-  ASSERT_EXIT(RangeSet::Parse("2,2,1"), ::testing::KilledBySignal(SIGABRT), "");
+  ASSERT_FALSE(RangeSet::Parse("2,2,2"));
+  ASSERT_FALSE(RangeSet::Parse("2,2,1"));
+}
+
+TEST(RangeSetTest, Clear) {
+  RangeSet rs = RangeSet::Parse("2,1,6");
+  ASSERT_TRUE(rs);
+  rs.Clear();
+  ASSERT_FALSE(rs);
+
+  // No-op to clear an empty RangeSet.
+  rs.Clear();
+  ASSERT_FALSE(rs);
+}
+
+TEST(RangeSetTest, PushBack) {
+  RangeSet rs;
+  ASSERT_FALSE(rs);
+
+  ASSERT_TRUE(rs.PushBack({ 3, 5 }));
+  ASSERT_EQ(RangeSet::Parse("2,3,5"), rs);
+
+  ASSERT_TRUE(rs.PushBack({ 5, 15 }));
+  ASSERT_EQ(RangeSet::Parse("4,3,5,5,15"), rs);
+  ASSERT_EQ(static_cast<size_t>(2), rs.size());
+  ASSERT_EQ(static_cast<size_t>(12), rs.blocks());
+}
+
+TEST(RangeSetTest, PushBack_InvalidInput) {
+  RangeSet rs;
+  ASSERT_FALSE(rs);
+  ASSERT_FALSE(rs.PushBack({ 5, 3 }));
+  ASSERT_FALSE(rs);
+  ASSERT_FALSE(rs.PushBack({ 15, 15 }));
+  ASSERT_FALSE(rs);
+
+  ASSERT_TRUE(rs.PushBack({ 5, 15 }));
+  ASSERT_FALSE(rs.PushBack({ 5, std::numeric_limits<size_t>::max() - 2 }));
+  ASSERT_EQ(RangeSet::Parse("2,5,15"), rs);
 }
 
 TEST(RangeSetTest, Overlaps) {
@@ -90,7 +139,7 @@
   ASSERT_NE(RangeSet::Parse("2,1,6"), RangeSet::Parse("2,1,7"));
   ASSERT_NE(RangeSet::Parse("2,1,6"), RangeSet::Parse("2,2,7"));
 
-  // The orders of Range's matter. "4,1,5,8,10" != "4,8,10,1,5".
+  // The orders of Range's matter, e.g. "4,1,5,8,10" != "4,8,10,1,5".
   ASSERT_NE(RangeSet::Parse("4,1,5,8,10"), RangeSet::Parse("4,8,10,1,5"));
 }
 
@@ -111,13 +160,14 @@
   ASSERT_EQ((std::vector<Range>{ Range{ 8, 10 }, Range{ 1, 5 } }), ranges);
 }
 
-TEST(RangeSetTest, tostring) {
+TEST(RangeSetTest, ToString) {
+  ASSERT_EQ("", RangeSet::Parse("").ToString());
   ASSERT_EQ("2,1,6", RangeSet::Parse("2,1,6").ToString());
   ASSERT_EQ("4,1,5,8,10", RangeSet::Parse("4,1,5,8,10").ToString());
   ASSERT_EQ("6,1,3,4,6,15,22", RangeSet::Parse("6,1,3,4,6,15,22").ToString());
 }
 
-TEST(SortedRangeSetTest, insertion) {
+TEST(SortedRangeSetTest, Insert) {
   SortedRangeSet rs({ { 2, 3 }, { 4, 6 }, { 8, 14 } });
   rs.Insert({ 1, 2 });
   ASSERT_EQ(SortedRangeSet({ { 1, 3 }, { 4, 6 }, { 8, 14 } }), rs);
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index 6c7b3ef..1c931af 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -492,6 +492,10 @@
   }
 
   RangeSet src = RangeSet::Parse(params.tokens[pos++]);
+  if (!src) {
+    LOG(ERROR) << "Failed to parse range in " << params.cmdline;
+    return;
+  }
 
   RangeSet locs;
   // If there's no stashed blocks, content in the buffer is consecutive and has the same
@@ -936,6 +940,7 @@
     params.cpos++;
   } else {
     RangeSet src = RangeSet::Parse(params.tokens[params.cpos++]);
+    CHECK(static_cast<bool>(src));
     *overlap = src.Overlaps(tgt);
 
     if (ReadBlocks(src, params.buffer, params.fd) == -1) {
@@ -948,6 +953,7 @@
     }
 
     RangeSet locs = RangeSet::Parse(params.tokens[params.cpos++]);
+    CHECK(static_cast<bool>(locs));
     MoveRange(params.buffer, locs, params.buffer);
   }
 
@@ -970,6 +976,7 @@
     }
 
     RangeSet locs = RangeSet::Parse(tokens[1]);
+    CHECK(static_cast<bool>(locs));
     MoveRange(params.buffer, locs, stash);
   }
 
@@ -1034,6 +1041,7 @@
 
   // <tgt_range>
   tgt = RangeSet::Parse(params.tokens[params.cpos++]);
+  CHECK(static_cast<bool>(tgt));
 
   std::vector<uint8_t> tgtbuffer(tgt.blocks() * BLOCKSIZE);
   if (ReadBlocks(tgt, tgtbuffer, params.fd) == -1) {
@@ -1146,6 +1154,7 @@
   }
 
   RangeSet src = RangeSet::Parse(params.tokens[params.cpos++]);
+  CHECK(static_cast<bool>(src));
 
   allocate(src.blocks() * BLOCKSIZE, params.buffer);
   if (ReadBlocks(src, params.buffer, params.fd) == -1) {
@@ -1196,6 +1205,7 @@
   }
 
   RangeSet tgt = RangeSet::Parse(params.tokens[params.cpos++]);
+  CHECK(static_cast<bool>(tgt));
 
   LOG(INFO) << "  zeroing " << tgt.blocks() << " blocks";
 
@@ -1238,6 +1248,7 @@
   }
 
   RangeSet tgt = RangeSet::Parse(params.tokens[params.cpos++]);
+  CHECK(static_cast<bool>(tgt));
 
   if (params.canwrite) {
     LOG(INFO) << " writing " << tgt.blocks() << " blocks of new data";
@@ -1368,6 +1379,7 @@
   }
 
   RangeSet tgt = RangeSet::Parse(params.tokens[params.cpos++]);
+  CHECK(static_cast<bool>(tgt));
 
   if (params.canwrite) {
     LOG(INFO) << " erasing " << tgt.blocks() << " blocks";
@@ -1773,6 +1785,7 @@
   }
 
   RangeSet rs = RangeSet::Parse(ranges->data);
+  CHECK(static_cast<bool>(rs));
 
   SHA_CTX ctx;
   SHA1_Init(&ctx);
@@ -1884,6 +1897,11 @@
     ErrorAbort(state, kArgsParsingFailure, "ranges argument to %s must be string", name);
     return StringValue("");
   }
+  RangeSet rs = RangeSet::Parse(ranges->data);
+  if (!rs) {
+    ErrorAbort(state, kArgsParsingFailure, "failed to parse ranges: %s", ranges->data.c_str());
+    return StringValue("");
+  }
 
   // Output notice to log when recover is attempted
   LOG(INFO) << filename->data << " image corrupted, attempting to recover...";
@@ -1909,7 +1927,7 @@
   }
 
   uint8_t buffer[BLOCKSIZE];
-  for (const auto& range : RangeSet::Parse(ranges->data)) {
+  for (const auto& range : rs) {
     for (size_t j = range.first; j < range.second; ++j) {
       // Stay within the data area, libfec validates and corrects metadata
       if (status.data_size <= static_cast<uint64_t>(j) * BLOCKSIZE) {