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List:       binutils-cvs
Subject:    [binutils-gdb] ELF core file size checks
From:       Alan Modra via Binutils-cvs <binutils-cvs () sourceware ! org>
Date:       2021-10-29 7:37:02
Message-ID: 20211029073702.11D67385743F () sourceware ! org
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https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=c45c3dba8cc80a41c4e0839df43c435c7aa0996d

commit c45c3dba8cc80a41c4e0839df43c435c7aa0996d
Author: Alan Modra <amodra@gmail.com>
Date:   Fri Oct 29 15:09:52 2021 +1030

    ELF core file size checks
    
    Catch fuzzed segments where p_offset + p_filesz wraps, and limit error
    output.
    
            * elfcore.h (elf_core_file_p): Rewrite segment checks using
            bfd_get_file_size.  Set read_only on file size errors.
            * elfcode.h (elf_swap_shdr_in): Don't repeat error message.

Diff:
---
 bfd/elfcode.h |  5 +++--
 bfd/elfcore.h | 39 ++++++++++++++++-----------------------
 2 files changed, 19 insertions(+), 25 deletions(-)

diff --git a/bfd/elfcode.h b/bfd/elfcode.h
index 7eb27c2e16d..ee88fce487d 100644
--- a/bfd/elfcode.h
+++ b/bfd/elfcode.h
@@ -325,9 +325,10 @@ elf_swap_shdr_in (bfd *abfd,
 	  && ((ufile_ptr) dst->sh_offset > filesize
 	      || dst->sh_size > filesize - dst->sh_offset))
 	{
+	  if (!abfd->read_only)
+	    _bfd_error_handler (_("warning: %pB has a section "
+				  "extending past end of file"), abfd);
 	  abfd->read_only = 1;
-	  _bfd_error_handler (_("warning: %pB has a section "
-				"extending past end of file"), abfd);
 	}
     }
   dst->sh_link = H_GET_32 (abfd, src->sh_link);
diff --git a/bfd/elfcore.h b/bfd/elfcore.h
index c0cdceba42a..832818f6cd1 100644
--- a/bfd/elfcore.h
+++ b/bfd/elfcore.h
@@ -92,6 +92,7 @@ elf_core_file_p (bfd *abfd)
   unsigned int phindex;
   const struct elf_backend_data *ebd;
   bfd_size_type amt;
+  ufile_ptr filesize;
 
   /* Read in the ELF header in external format.  */
   if (bfd_bread (&x_ehdr, sizeof (x_ehdr), abfd) != sizeof (x_ehdr))
@@ -286,29 +287,21 @@ elf_core_file_p (bfd *abfd)
       goto fail;
 
   /* Check for core truncation.  */
-  {
-    bfd_size_type high = 0;
-    struct stat statbuf;
-    for (phindex = 0; phindex < i_ehdrp->e_phnum; ++phindex)
-      {
-	Elf_Internal_Phdr *p = i_phdrp + phindex;
-	if (p->p_filesz)
-	  {
-	    bfd_size_type current = p->p_offset + p->p_filesz;
-	    if (high < current)
-	      high = current;
-	  }
-      }
-    if (bfd_stat (abfd, &statbuf) == 0)
-      {
-	if ((bfd_size_type) statbuf.st_size < high)
-	  {
-	    _bfd_error_handler
-	      /* xgettext:c-format */
-	      (_("warning: %pB is truncated: expected core file "
-		 "size >= %" PRIu64 ", found: %" PRIu64),
-	       abfd, (uint64_t) high, (uint64_t) statbuf.st_size);
-	  }
+  filesize = bfd_get_file_size (abfd);
+  if (filesize != 0)
+    {
+      for (phindex = 0; phindex < i_ehdrp->e_phnum; ++phindex)
+	{
+	  Elf_Internal_Phdr *p = i_phdrp + phindex;
+	  if (p->p_filesz
+	      && (p->p_offset >= filesize
+		  || p->p_filesz > filesize - p->p_offset))
+	    {
+	      _bfd_error_handler (_("warning: %pB has a segment "
+				    "extending past end of file"), abfd);
+	      abfd->read_only = 1;
+	      break;
+	    }
       }
   }
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