[PATCH] D25315: [Object/ELF] - Do section header sh_offset/sh_size values check once during object loading.

[George Rimar via llvm-commits]

grimar created this revision.
grimar added reviewers: rafael, davide.
grimar added subscribers: llvm-commits, grimar, evgeny777.

This helps to keep client code cleaner. 
For example we have next code in LLD:

  auto *Begin =
      reinterpret_cast<const Elf_Dyn *>(Obj.base() + DynamicSec->sh_offset);
  const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);

sh_offset and/or sh_size may be broken here and the same situation can be found for some other sections.
Instead of placing multiple checks in LLD, I suggest this change to check object once during loading.


https://reviews.llvm.org/D25315

Files:
  include/llvm/Object/ELF.h
  test/Object/Inputs/invalid-relocation-sec-sh_size.elf-i386
  test/Object/Inputs/invalid-relocation-sec-sh_size.elf-x86-64
  test/Object/invalid.test


Index: test/Object/invalid.test
===================================================================
--- test/Object/invalid.test
+++ test/Object/invalid.test
@@ -63,4 +63,10 @@
 RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-OFFSET %s
 RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_offset.elf-x86-64 2>&1 | \
 RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-OFFSET %s
-INVALID-RELOC-SH-OFFSET: Invalid relocation entry offset
+INVALID-RELOC-SH-OFFSET: Invalid data was encountered while parsing the file
+
+RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_size.elf-i386 2>&1 | \
+RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-SIZE %s
+RUN: not llvm-readobj -r %p/Inputs/invalid-relocation-sec-sh_size.elf-x86-64 2>&1 | \
+RUN:   FileCheck --check-prefix=INVALID-RELOC-SH-SIZE %s
+INVALID-RELOC-SH-SIZE: Invalid data was encountered while parsing the file
Index: include/llvm/Object/ELF.h
===================================================================
--- include/llvm/Object/ELF.h
+++ include/llvm/Object/ELF.h
@@ -137,8 +137,6 @@
   const Elf_Rela *rela_begin(const Elf_Shdr *sec) const {
     if (sec->sh_entsize != sizeof(Elf_Rela))
       report_fatal_error("Invalid relocation entry size");
-    if (sec->sh_offset >= Buf.size())
-      report_fatal_error("Invalid relocation entry offset");
     return reinterpret_cast<const Elf_Rela *>(base() + sec->sh_offset);
   }
 
@@ -156,8 +154,6 @@
   const Elf_Rel *rel_begin(const Elf_Shdr *sec) const {
     if (sec->sh_entsize != sizeof(Elf_Rel))
       report_fatal_error("Invalid relocation entry size");
-    if (sec->sh_offset >= Buf.size())
-      report_fatal_error("Invalid relocation entry offset");
     return reinterpret_cast<const Elf_Rel *>(base() + sec->sh_offset);
   }
 
@@ -385,6 +381,14 @@
     DotShstrtab = *StringTableOrErr;
   }
 
+  for (const Elf_Shdr &Sec : sections()) {
+    if ((Sec.sh_offset > getBufSize()) ||
+      (Sec.sh_offset + Sec.sh_size > getBufSize())) {
+      EC = object_error::parse_failed;
+      return;
+    }
+  }
+
   EC = std::error_code();
 }
 


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