From 519c13c9c7fc591609eed405a3e952707c60ec7e Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mjw@redhat.com>
Date: Wed, 30 Dec 2015 01:39:29 +0100
Subject: libelf: Make elf_strptr index correctly into compressed section data.

elf_strptr indexes into the section data. This is defined as index into
the uncompressed data of the section. If the section is compressed make
sure the uncompressed data is available, but don't really decompress the
section header (elf_getdata will still return compressed data).

Signed-off-by: Mark Wielaard <mjw@redhat.com>
---
 libelf/elf_compress.c | 97 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 59 insertions(+), 38 deletions(-)

(limited to 'libelf/elf_compress.c')

diff --git a/libelf/elf_compress.c b/libelf/elf_compress.c
index 17b80f2d..ec5b7174 100644
--- a/libelf/elf_compress.c
+++ b/libelf/elf_compress.c
@@ -248,6 +248,47 @@ __libelf_decompress (void *buf_in, size_t size_in, size_t size_out)
   return buf_out;
 }
 
+void *
+internal_function
+__libelf_decompress_elf (Elf_Scn *scn, size_t *size_out, size_t *addralign)
+{
+  GElf_Chdr chdr;
+  if (gelf_getchdr (scn, &chdr) == NULL)
+    return NULL;
+
+  if (chdr.ch_type != ELFCOMPRESS_ZLIB)
+    {
+      __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
+      return NULL;
+    }
+
+  if (! powerof2 (chdr.ch_addralign))
+    {
+      __libelf_seterrno (ELF_E_INVALID_ALIGN);
+      return NULL;
+    }
+
+  /* Take the in-memory representation, so we can even handle a
+     section that has just been constructed (maybe it was copied
+     over from some other ELF file first with elf_newdata).  This
+     is slightly inefficient when the raw data needs to be
+     converted since then we'll be converting the whole buffer and
+     not just Chdr.  */
+  Elf_Data *data = elf_getdata (scn, NULL);
+  if (data == NULL)
+    return NULL;
+
+  int elfclass = scn->elf->class;
+  size_t hsize = (elfclass == ELFCLASS32
+		  ? sizeof (Elf32_Chdr) : sizeof (Elf64_Chdr));
+  size_t size_in = data->d_size - hsize;
+  void *buf_in = data->d_buf + hsize;
+  void *buf_out = __libelf_decompress (buf_in, size_in, chdr.ch_size);
+  *size_out = chdr.ch_size;
+  *addralign = chdr.ch_addralign;
+  return buf_out;
+}
+
 void
 internal_function
 __libelf_reset_rawdata (Elf_Scn *scn, void *buf, size_t size, size_t align,
@@ -424,62 +465,42 @@ elf_compress (Elf_Scn *scn, int type, unsigned int flags)
 	  return -1;
 	}
 
-      GElf_Chdr chdr;
-      if (gelf_getchdr (scn, &chdr) == NULL)
-	return -1;
-
-      if (chdr.ch_type != ELFCOMPRESS_ZLIB)
+      /* If the data is already decompressed (by elf_strptr), then we
+	 only need to setup the rawdata and section header. XXX what
+	 about elf_newdata?  */
+      if (scn->zdata_base == NULL)
 	{
-	  __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
-	  return -1;
+	  size_t size_out, addralign;
+	  void *buf_out = __libelf_decompress_elf (scn, &size_out, &addralign);
+	  if (buf_out == NULL)
+	    return -1;
+
+	  scn->zdata_base = buf_out;
+	  scn->zdata_size = size_out;
+	  scn->zdata_align = addralign;
 	}
 
-      if (! powerof2 (chdr.ch_addralign))
-	{
-	  __libelf_seterrno (ELF_E_INVALID_ALIGN);
-	  return -1;
-	}
-
-      /* Take the in-memory representation, so we can even handle a
-	 section that has just been constructed (maybe it was copied
-	 over from some other ELF file first with elf_newdata).  This
-	 is slightly inefficient when the raw data needs to be
-	 converted since then we'll be converting the whole buffer and
-	 not just Chdr.  */
-      Elf_Data *data = elf_getdata (scn, NULL);
-      if (data == NULL)
-	return -1;
-
-      size_t hsize = (elfclass == ELFCLASS32
-		      ? sizeof (Elf32_Chdr) : sizeof (Elf64_Chdr));
-      size_t size_in = data->d_size - hsize;
-      void *buf_in = data->d_buf + hsize;
-      void *buf_out = __libelf_decompress (buf_in, size_in, chdr.ch_size);
-      if (buf_out == NULL)
-	return -1;
-
       /* Note we keep the sh_entsize as is, we assume it is setup
 	 correctly and ignored when SHF_COMPRESSED is set.  */
       if (elfclass == ELFCLASS32)
 	{
 	  Elf32_Shdr *shdr = elf32_getshdr (scn);
-	  shdr->sh_size = chdr.ch_size;
-	  shdr->sh_addralign = chdr.ch_addralign;
+	  shdr->sh_size = scn->zdata_size;
+	  shdr->sh_addralign = scn->zdata_align;
 	  shdr->sh_flags &= ~SHF_COMPRESSED;
 	}
       else
 	{
 	  Elf64_Shdr *shdr = elf64_getshdr (scn);
-	  shdr->sh_size = chdr.ch_size;
-	  shdr->sh_addralign = chdr.ch_addralign;
+	  shdr->sh_size = scn->zdata_size;
+	  shdr->sh_addralign = scn->zdata_align;
 	  shdr->sh_flags &= ~SHF_COMPRESSED;
 	}
 
-      __libelf_reset_rawdata (scn, buf_out, chdr.ch_size, chdr.ch_addralign,
+      __libelf_reset_rawdata (scn, scn->zdata_base,
+			      scn->zdata_size, scn->zdata_align,
 			      __libelf_data_type (elf, sh_type));
 
-      scn->zdata_base = buf_out;
-
       return 1;
     }
   else
-- 
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