[llvm-branch-commits] [llvm] b8cb180 - [obj2yaml] - Dump the content of a broken GNU hash table properly.

[Georgii Rymar via llvm-branch-commits]

Author: Georgii Rymar
Date: 2020-12-24T11:16:31+03:00
New Revision: b8cb1802a8a2037bd893e038b4eafa61bd5c279e

URL: https://github.com/llvm/llvm-project/commit/b8cb1802a8a2037bd893e038b4eafa61bd5c279e
DIFF: https://github.com/llvm/llvm-project/commit/b8cb1802a8a2037bd893e038b4eafa61bd5c279e.diff

LOG: [obj2yaml] - Dump the content of a broken GNU hash table properly.

When something is wrong with the GNU hash table header we dump
its context as a raw data.

Currently we have the calculation overflow issue and it is possible to
bypass the validation we have (and crash).

The patch fixes it.

Differential revision: https://reviews.llvm.org/D93760

Added: 
    

Modified: 
    llvm/test/tools/obj2yaml/ELF/gnu-hash-section.yaml
    llvm/tools/obj2yaml/elf2yaml.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/test/tools/obj2yaml/ELF/gnu-hash-section.yaml b/llvm/test/tools/obj2yaml/ELF/gnu-hash-section.yaml
index 7dd0a7c870ea..00861c013100 100644
--- a/llvm/test/tools/obj2yaml/ELF/gnu-hash-section.yaml
+++ b/llvm/test/tools/obj2yaml/ELF/gnu-hash-section.yaml
@@ -54,9 +54,12 @@ Sections:
 # INVALID-NEXT: - Name:        .gnu.hash.broken.maskwords
 # INVALID-NEXT:   Type:        SHT_GNU_HASH
 # INVALID-NEXT:   Content:     '00000000000000000100000000000000'
-# INVALID-NEXT: - Name:        .gnu.hash.broken.nbuckets
+# INVALID-NEXT: - Name:        .gnu.hash.broken.nbuckets.a
 # INVALID-NEXT:   Type:        SHT_GNU_HASH
 # INVALID-NEXT:   Content:     '01000000000000000000000000000000'
+# INVALID-NEXT: - Name:        .gnu.hash.broken.nbuckets.b
+# INVALID-NEXT:   Type:        SHT_GNU_HASH
+# INVALID-NEXT:   Content:     FFFFFFFF000000000100000000000000{{$}}
 # INVALID-NEXT: - Name:        .gnu.hash.hashvalues.ok
 # INVALID-NEXT:   Type:        SHT_GNU_HASH
 # INVALID-NEXT:   Header:
@@ -108,9 +111,9 @@ Sections:
     BloomFilter: []
     HashBuckets: []
     HashValues:  []
-## Case 4: NBuckets field is broken, it says that the number of entries
+## Case 4(a): NBuckets field is broken, it says that the number of entries
 ## in the hash buckets is 1, but it is empty.
-  - Name:  .gnu.hash.broken.nbuckets
+  - Name:  .gnu.hash.broken.nbuckets.a
     Type:  SHT_GNU_HASH
     Header:
       SymNdx: 0x0
@@ -120,6 +123,18 @@ Sections:
     BloomFilter: []
     HashBuckets: []
     HashValues:  []
+## Case 4(b): NBuckets = 0xFFFFFFFF is incorrect. The result will cause 32-bit
+## unsigned overflows if we keep intermediate expressions uint32_t.
+  - Name:  .gnu.hash.broken.nbuckets.b
+    Type:  SHT_GNU_HASH
+    Header:
+      SymNdx: 0x0
+      Shift2: 0x0
+      MaskWords: 0x1
+      NBuckets:  0xFFFFFFFF
+    BloomFilter: []
+    HashBuckets: []
+    HashValues:  []
 ## Case 5: Check that we use the various properties to dump the data when it
 ## has a size that is a multiple of 4, but fallback to dumping the whole section
 ## using the "Content" property otherwise.

diff  --git a/llvm/tools/obj2yaml/elf2yaml.cpp b/llvm/tools/obj2yaml/elf2yaml.cpp
index 1f9ff88f042a..2b54acd99f9e 100644
--- a/llvm/tools/obj2yaml/elf2yaml.cpp
+++ b/llvm/tools/obj2yaml/elf2yaml.cpp
@@ -1271,9 +1271,9 @@ ELFDumper<ELFT>::dumpGnuHashSection(const Elf_Shdr *Shdr) {
 
   ELFYAML::GnuHashHeader Header;
   DataExtractor::Cursor Cur(0);
-  uint32_t NBuckets = Data.getU32(Cur);
+  uint64_t NBuckets = Data.getU32(Cur);
   Header.SymNdx = Data.getU32(Cur);
-  uint32_t MaskWords = Data.getU32(Cur);
+  uint64_t MaskWords = Data.getU32(Cur);
   Header.Shift2 = Data.getU32(Cur);
 
   // Set just the raw binary content if we were unable to read the header