File use-the-empty-string-for-note-names-with-zero-size.patch of Package elfutils.8903

From: Mark Wielaard <mark at klomp dot org>
To: elfutils-devel at sourceware dot org
Cc: Mark Wielaard <mark at klomp dot org>
Date: Fri, 24 Mar 2017 14:10:26 +0100
Subject: [PATCH] Use the empty string for note names with zero size (without any
  data).
Reference: bnc#1033085

ELF notes can have a zero sized name. In which case there is no data at
all (so also no zero terminator). Make sure to use the empty string for
such notes if the code does not otherwise explicitly check n_namesz.

https://sourceware.org/bugzilla/show_bug.cgi?id=21300

elfutils packaging edits:
 - changelog hunk removed from original patch to avoid conflict

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdwfl/linux-core-attach.c | 9 ++++++---
 src/elfcmp.c                | 6 ++++--
 src/readelf.c               | 2 +-
 5 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/libdwfl/linux-core-attach.c b/libdwfl/linux-core-attach.c
index 93d0e46..f82ed03 100644
--- a/libdwfl/linux-core-attach.c
+++ b/libdwfl/linux-core-attach.c
@@ -125,7 +125,8 @@ core_next_thread (Dwfl *dwfl __attribute__ ((unused)), void *dwfl_arg,
 							  &desc_offset)) > 0)
     {
       /* Do not check NAME for now, help broken Linux kernels.  */
-      const char *name = note_data->d_buf + name_offset;
+      const char *name = (nhdr.n_namesz == 0
+			  ? "" : note_data->d_buf + name_offset);
       const char *desc = note_data->d_buf + desc_offset;
       GElf_Word regs_offset;
       size_t nregloc;
@@ -178,7 +179,8 @@ core_set_initial_registers (Dwfl_Thread *thread, void *thread_arg_voidp)
   /* __libdwfl_attach_state_for_core already verified the note is there.  */
   assert (getnote_err != 0);
   /* Do not check NAME for now, help broken Linux kernels.  */
-  const char *name = note_data->d_buf + name_offset;
+  const char *name = (nhdr.n_namesz == 0
+		      ? "" : note_data->d_buf + name_offset);
   const char *desc = note_data->d_buf + desc_offset;
   GElf_Word regs_offset;
   size_t nregloc;
@@ -367,7 +369,8 @@ dwfl_core_file_attach (Dwfl *dwfl, Elf *core)
 				    &nhdr, &name_offset, &desc_offset)) > 0)
     {
       /* Do not check NAME for now, help broken Linux kernels.  */
-      const char *name = note_data->d_buf + name_offset;
+      const char *name = (nhdr.n_namesz == 0
+			  ? "" : note_data->d_buf + name_offset);
       const char *desc = note_data->d_buf + desc_offset;
       GElf_Word regs_offset;
       size_t nregloc;

diff --git a/src/elfcmp.c b/src/elfcmp.c
index 7673cf2..5046420 100644
--- a/src/elfcmp.c
+++ b/src/elfcmp.c
@@ -419,7 +419,8 @@ main (int argc, char *argv[])
 		   && (off1 = gelf_getnote (data1, off1, &note1,
 					    &name_offset, &desc_offset)) > 0)
 	      {
-		const char *name1 = data1->d_buf + name_offset;
+		const char *name1 = (note1.n_namesz == 0
+				     ? "" : data1->d_buf + name_offset);
 		const void *desc1 = data1->d_buf + desc_offset;
 		if (off2 >= data2->d_size)
 		  {
@@ -435,7 +436,8 @@ main (int argc, char *argv[])
 		  error (2, 0, gettext ("\
 cannot read note section [%zu] '%s' in '%s': %s"),
 			 elf_ndxscn (scn2), sname2, fname2, elf_errmsg (-1));
-		const char *name2 = data2->d_buf + name_offset;
+		const char *name2 = (note2.n_namesz == 0
+				     ? "" : data2->d_buf + name_offset);
 		const void *desc2 = data2->d_buf + desc_offset;
 
 		if (note1.n_namesz != note2.n_namesz
diff --git a/src/readelf.c b/src/readelf.c
index 490b6d5..97a43b0 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -9365,7 +9365,7 @@ handle_notes_data (Ebl *ebl, const GElf_Ehdr *ehdr,
 	 && (offset = gelf_getnote (data, offset,
 				    &nhdr, &name_offset, &desc_offset)) > 0)
     {
-      const char *name = data->d_buf + name_offset;
+      const char *name = nhdr.n_namesz == 0 ? "" : data->d_buf + name_offset;
       const char *desc = data->d_buf + desc_offset;
 
       char buf[100];
-- 
1.8.3.1
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