[PATCH] readelf: Save and dump the original section header values

From aa021d0f19e7a871aa3d976587697f8b12a073bd Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <[email protected]>
Date: Thu, 2 Jul 2026 10:14:10 +0800
Subject: [PATCH] readelf: Save and dump the original section header values

validate_section_info clears the garbage values in the section header
to avoid crash later.  Save and dump the original section header values
to make the garbage values in the section header visible when dumping
section headers.

	* readelf.c (filedata): Add orig_section_headers.
	(validate_section_info): Add a pointer to the original section
	header and save the original section header values.
	(get_32bit_section_headers): Allocate the original section header
	buffer.  Pass the original section header pointer to
	validate_section_info.
	(get_64bit_section_headers): Likewise.
	(process_section_headers): Dump the original section headers.
	(process_relocs): Pass a dummy original section pointer to
	validate_section_info.
	(free_filedata): Free filedata->orig_section_headers.
	* testsuite/binutils-all/corrupt-1.elf.bz2: New file.
	* testsuite/binutils-all/corrupt-1.r: Likewise.
	* testsuite/binutils-all/readelf.exp: Run corrupt-1.elf test.

Signed-off-by: H.J. Lu <[email protected]>
---
 binutils/readelf.c                            |  54 +++++++++++++++---
 .../testsuite/binutils-all/corrupt-1.elf.bz2  | Bin 0 -> 81 bytes
 binutils/testsuite/binutils-all/corrupt-1.r   |   3 +
 binutils/testsuite/binutils-all/readelf.exp   |  12 ++++
 4 files changed, 61 insertions(+), 8 deletions(-)
 create mode 100644 binutils/testsuite/binutils-all/corrupt-1.elf.bz2
 create mode 100644 binutils/testsuite/binutils-all/corrupt-1.r

diff --git a/binutils/readelf.c b/binutils/readelf.c
index 2826e0cf195..ea679b3b4f4 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -282,6 +282,7 @@ typedef struct filedata
   uint64_t             archive_file_size;
   /* Everything below this point is cleared out by free_filedata.  */
   Elf_Internal_Shdr *  section_headers;
+  Elf_Internal_Shdr *  orig_section_headers;
   Elf_Internal_Phdr *  program_headers;
   char *               string_table;
   uint64_t             string_table_length;
@@ -7851,12 +7852,16 @@ offset_from_vma (Filedata * filedata, uint64_t vma, uint64_t size)
 /* Valid section info and clear the invalid fields.  */
 
 static void
-validate_section_info (Elf_Internal_Shdr *internal, unsigned int i,
+validate_section_info (Elf_Internal_Shdr *internal,
+		       Elf_Internal_Shdr *orig_internal, unsigned int i,
 		       Filedata *filedata, bool dynamic, bool probe)
 {
   const char *dynamic_tag = NULL;
   const char *dynamicsz_tag = NULL;
   const char *dynamicent_tag = NULL;
+  /* Save the original section header values before garbage values are
+     cleared.  */
+  *orig_internal = *internal;
   if (probe)
     return;
 
@@ -7944,6 +7949,7 @@ get_32bit_section_headers (Filedata * filedata, bool probe)
 {
   Elf32_External_Shdr * shdrs;
   Elf_Internal_Shdr *   internal;
+  Elf_Internal_Shdr *   orig_internal;
   unsigned int          i;
   unsigned int          size = filedata->file_header.e_shentsize;
   unsigned int          num = probe ? 1 : filedata->file_header.e_shnum;
@@ -7983,9 +7989,22 @@ get_32bit_section_headers (Filedata * filedata, bool probe)
       return false;
     }
 
+  filedata->orig_section_headers = (Elf_Internal_Shdr *)
+    cmalloc (num, sizeof (Elf_Internal_Shdr));
+  if (filedata->orig_section_headers == NULL)
+    {
+      if (!probe)
+	error (_("Out of memory reading %u section headers\n"), num);
+      free (shdrs);
+      free (filedata->section_headers);
+      filedata->section_headers = NULL;
+      return false;
+    }
+
+  orig_internal = filedata->orig_section_headers;
   for (i = 0, internal = filedata->section_headers;
        i < num;
-       i++, internal++)
+       i++, internal++, orig_internal++)
     {
       internal->sh_name      = BYTE_GET (shdrs[i].sh_name);
       internal->sh_type      = BYTE_GET (shdrs[i].sh_type);
@@ -7997,7 +8016,8 @@ get_32bit_section_headers (Filedata * filedata, bool probe)
       internal->sh_info      = BYTE_GET (shdrs[i].sh_info);
       internal->sh_addralign = BYTE_GET (shdrs[i].sh_addralign);
       internal->sh_entsize   = BYTE_GET (shdrs[i].sh_entsize);
-      validate_section_info (internal, i, filedata, false, probe);
+      validate_section_info (internal, orig_internal, i, filedata,
+			     false, probe);
     }
 
   free (shdrs);
@@ -8011,6 +8031,7 @@ get_64bit_section_headers (Filedata * filedata, bool probe)
 {
   Elf64_External_Shdr *  shdrs;
   Elf_Internal_Shdr *    internal;
+  Elf_Internal_Shdr *    orig_internal;
   unsigned int           i;
   unsigned int           size = filedata->file_header.e_shentsize;
   unsigned int           num = probe ? 1 : filedata->file_header.e_shnum;
@@ -8052,9 +8073,22 @@ get_64bit_section_headers (Filedata * filedata, bool probe)
       return false;
     }
 
+  filedata->orig_section_headers = (Elf_Internal_Shdr *)
+    cmalloc (num, sizeof (Elf_Internal_Shdr));
+  if (filedata->orig_section_headers == NULL)
+    {
+      if (!probe)
+	error (_("Out of memory reading %u section headers\n"), num);
+      free (shdrs);
+      free (filedata->section_headers);
+      filedata->section_headers = NULL;
+      return false;
+    }
+
+  orig_internal = filedata->orig_section_headers;
   for (i = 0, internal = filedata->section_headers;
        i < num;
-       i++, internal++)
+       i++, internal++, orig_internal++)
     {
       internal->sh_name      = BYTE_GET (shdrs[i].sh_name);
       internal->sh_type      = BYTE_GET (shdrs[i].sh_type);
@@ -8066,7 +8100,8 @@ get_64bit_section_headers (Filedata * filedata, bool probe)
       internal->sh_info      = BYTE_GET (shdrs[i].sh_info);
       internal->sh_offset    = BYTE_GET (shdrs[i].sh_offset);
       internal->sh_addralign = BYTE_GET (shdrs[i].sh_addralign);
-      validate_section_info (internal, i, filedata, false, probe);
+      validate_section_info (internal, orig_internal, i, filedata,
+			     false, probe);
     }
 
   free (shdrs);
@@ -9016,7 +9051,8 @@ process_section_headers (Filedata * filedata)
   if (do_section_details)
     printf (_("       Flags\n"));
 
-  for (i = 0, section = filedata->section_headers;
+  /* Dump the original section headers.  */
+  for (i = 0, section = filedata->orig_section_headers;
        i < filedata->file_header.e_shnum;
        i++, section++)
     {
@@ -10197,13 +10233,14 @@ process_relocs (Filedata * filedata)
 		  uint64_t num_reloc;
 		  uint64_t *relrs = NULL;
 		  Elf_Internal_Shdr section = {};
+		  Elf_Internal_Shdr orig_section;
 		  section.sh_offset
 		    = filedata->dynamic_info[DT_RELR];
 		  section.sh_size = rel_size;
 		  section.sh_entsize = rel_entsz;
 		  section.sh_type = SHT_RELR;
-		  validate_section_info (&section, DT_RELR, filedata,
-					 true, false);
+		  validate_section_info (&section, &orig_section, DT_RELR,
+					 filedata, true, false);
 		  num_reloc = count_relr_relocations (filedata,
 						      &section,
 						      &relrs);
@@ -24847,6 +24884,7 @@ free_filedata (Filedata *filedata)
   free (filedata->program_interpreter);
   free (filedata->program_headers);
   free (filedata->section_headers);
+  free (filedata->orig_section_headers);
   free (filedata->string_table);
   free (filedata->dump.dump_sects);
   free (filedata->dynamic_strings);
diff --git a/binutils/testsuite/binutils-all/corrupt-1.elf.bz2 b/binutils/testsuite/binutils-all/corrupt-1.elf.bz2
new file mode 100644
index 0000000000000000000000000000000000000000..e9c9f44343a4aadd90457df5e49923830881d194
GIT binary patch
literal 81
zcmV-X0IvT+T4*^jL0KkKS<!e4e*gd?Wun|A06@b80RR91fItKQfCwM}Ata_F&>`e0
nlM^7w$`z$$Gahz<VUjiOf0D@DL^^qw1A^{IrwS4pF9C1h02mvG

literal 0
HcmV?d00001

diff --git a/binutils/testsuite/binutils-all/corrupt-1.r b/binutils/testsuite/binutils-all/corrupt-1.r
new file mode 100644
index 00000000000..ae6438703e2
--- /dev/null
+++ b/binutils/testsuite/binutils-all/corrupt-1.r
@@ -0,0 +1,3 @@
+#...
+  \[10\] <no-strings>      REL             0000000000000000 000000 6666666666666600 00      0   0  0
+#pass
diff --git a/binutils/testsuite/binutils-all/readelf.exp b/binutils/testsuite/binutils-all/readelf.exp
index 0f3d75090b2..6c5e63fb9e8 100644
--- a/binutils/testsuite/binutils-all/readelf.exp
+++ b/binutils/testsuite/binutils-all/readelf.exp
@@ -612,6 +612,18 @@ if ![is_remote host] {
     } else {
 	readelf_test {-wi} $tempfile pr26160.r
     }
+
+    set test $srcdir/$subdir/corrupt-1.elf.bz2
+    # We need to strip the ".bz2", but can leave the dirname.
+    set t $subdir/[file tail $test]
+    set testname [file rootname $t]
+    verbose $testname
+    set tempfile tmpdir/corrupt-1.elf
+    if {[catch "system \"bzip2 -dc $test > $tempfile\""] != 0} {
+	untested "bzip2 -dc ($testname)"
+    } else {
+	readelf_test {-SW} $tempfile corrupt-1.r
+    }
 }
 
 # Check dwarf-5 support for DW_OP_addrx.
-- 
2.54.0