Don't try to read section headers if they're not present.

peadar · Sep 30, 2023 · 698f3e6 · 698f3e6
1 parent d06105a
commit 698f3e6
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Showing 3 changed files with 58 additions and 43 deletions.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -41,7 +41,7 @@ endif()
 set(VERSION_TAG ${GIT_TAG} CACHE STRING "Version tag (defaults to git commit)")
 message(STATUS "Version: ${VERSION_TAG}")
 
-add_definitions(-DVERSION=${VERSION_TAG} -D_FORTIFY_SOURCE=2)
+add_definitions(-DVERSION=${VERSION_TAG})
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_EXTENSIONS ON)

diff --git a/elf.cc b/elf.cc
@@ -223,50 +223,63 @@ Object::Object(ImageCache &cache, Reader::csptr io_, bool isDebug)
     Elf::Off off;
     int i;
 
-    // If there are too many headers, we need to look in the first section header
-    // to get the actual count.
-    int headerCount = elfHeader.e_shnum == 0 && elfHeader.e_shentsize != 0 ?
-       1 : elfHeader.e_shnum;
-
-    // sectionHeaders.reserve(elfHeader.e_shnum);
-    for (off = elfHeader.e_shoff, i = 0; i < headerCount; i++) {
-        sectionHeaders.emplace_back(std::make_unique<Section>(this, off));
-        if (i == 0 && elfHeader.e_shnum == 0)
-            headerCount = sectionHeaders[0]->shdr.sh_size;
-        off += elfHeader.e_shentsize;
-    }
-    if (sectionHeaders.size() == 0) {
-        sectionHeaders.push_back(std::make_unique<Section>());
-    }
-
-    if (elfHeader.e_shstrndx != SHN_UNDEF) {
-       // Create a mapping from section header names to section headers.
-       // We need to do this after reading all the section headers, because
-       // until then we don't have the details of the shstr section
+    // Make sure the header sections are present in the reader, otherwise, skip.
+    if (elfHeader.e_shoff < io->size()) {
+       // If there are too many headers, we need to look in the first section header
+       // to get the actual count.
        //
-       // We need to deal with the fact that e_shstrndx might be too small
-       // to hold the index of the string section, and look in sh_link if so.
-       int shstrSec = elfHeader.e_shstrndx == SHN_XINDEX ?
-           sectionHeaders[0]->shdr.sh_link :
-           elfHeader.e_shstrndx;
-       auto &sshdr = sectionHeaders[shstrSec];
-       size_t secid = 0;
-       for (auto &h : sectionHeaders) {
-           auto name = sshdr->io()->readString(h->shdr.sh_name);
-           namedSection[name] = secid++;
-           h->name = name;
+       int headerCount;
+       if (elfHeader.e_shnum == 0 && elfHeader.e_shentsize != 0) {
+          headerCount = 1;
+       } else {
+          headerCount = elfHeader.e_shnum;
+          sectionHeaders.reserve(headerCount);
        }
 
-       /*
-        * Load dynamic entries
-        */
-       auto &section = getSection(".dynamic", SHT_DYNAMIC );
-       if (section) {
-           ReaderArray<Dyn> content(*section.io());
-           for (auto dyn : content)
-              dynamic[dyn.d_tag].push_back(dyn);
+       for (off = elfHeader.e_shoff, i = 0; i < headerCount; i++) {
+           sectionHeaders.emplace_back(std::make_unique<Section>(this, off));
+           if (i == 0 && elfHeader.e_shnum == 0) {
+               headerCount = sectionHeaders[0]->shdr.sh_size;
+               sectionHeaders.reserve(headerCount);
+           }
+           off += elfHeader.e_shentsize;
+       }
+       if (sectionHeaders.size() == 0) {
+           sectionHeaders.push_back(std::make_unique<Section>());
        }
-       gnu_version = &getSection(".gnu_version", SHT_GNU_versym);
+
+       if (elfHeader.e_shstrndx != SHN_UNDEF) {
+          // Create a mapping from section header names to section headers.
+          // We need to do this after reading all the section headers, because
+          // until then we don't have the details of the shstr section
+          //
+          // We need to deal with the fact that e_shstrndx might be too small
+          // to hold the index of the string section, and look in sh_link if so.
+          int shstrSec = elfHeader.e_shstrndx == SHN_XINDEX ?
+              sectionHeaders[0]->shdr.sh_link :
+              elfHeader.e_shstrndx;
+          auto &sshdr = sectionHeaders[shstrSec];
+          size_t secid = 0;
+          for (auto &h : sectionHeaders) {
+              auto name = sshdr->io()->readString(h->shdr.sh_name);
+              namedSection[name] = secid++;
+              h->name = name;
+          }
+
+          /*
+           * Load dynamic entries
+           */
+          auto &section = getSection(".dynamic", SHT_DYNAMIC );
+          if (section) {
+              ReaderArray<Dyn> content(*section.io());
+              for (auto dyn : content)
+                 dynamic[dyn.d_tag].push_back(dyn);
+          }
+          gnu_version = &getSection(".gnu_version", SHT_GNU_versym);
+       }
+    } else {
+        // leave a null section no matter what.
+        sectionHeaders.push_back(std::make_unique<Section>());
     }
 }
 

diff --git a/libpstack/proc.h b/libpstack/proc.h
@@ -164,12 +164,14 @@ struct Lwp {
 
 struct PrintableFrame;
 
-
 struct DevNode {
     int major;
     int minor;
     unsigned long inode;
     std::string path;
+    bool operator == (const DevNode &rhs) {
+       return major == rhs.major && minor == rhs.minor && inode == rhs.inode;
+    }
 };
 
 struct AddressRange {
@@ -179,7 +181,7 @@ struct AddressRange {
    DevNode backing;
 
    enum class Flags { read,write,exec,priv,count, shared };
-   std::set<Flags> permissions; // PROT_READ/PROT_WRITE/PROT_EXEC
+   std::set<Flags> permissions;
 };
 
 class Process : public ps_prochandle {