[PATCH] libelf: Only memcpy ehdr back when not already directly mmapped.

Mark Wielaard mjw at redhat.com
Fri Nov 8 18:28:16 UTC 2013


When the elf file is mmapped ehdr can still point to ehdr_mem if the
address is unaligned.  In such cases we do need to memcpy the ehdr back
to the file. We shouldn't when ehdr already comes directly from the mmapped
file, because that would cause an memcpy call with overlapping addresses
(ehdr being copied directly over itself).

Signed-off-by: Mark Wielaard <mjw at redhat.com>
---
 libelf/ChangeLog          |    5 +++++
 libelf/elf32_updatefile.c |    2 +-
 2 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index a996ccf..148c945 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-08  Mark Wielaard  <mjw at redhat.com>
+
+	* elf32_updatefile.c (elfXX_updatemmap): Only memcpy ehdr when not
+	already directly mmapped.
+
 2013-11-05  Mark Wielaard  <mjw at redhat.com>
 
 	* elf32_updatefile.c (elfXX_updatefile): Copy all section headers
diff --git a/libelf/elf32_updatefile.c b/libelf/elf32_updatefile.c
index c4af9c0..b39e284 100644
--- a/libelf/elf32_updatefile.c
+++ b/libelf/elf32_updatefile.c
@@ -133,7 +133,7 @@ __elfw2(LIBELFBITS,updatemmap) (Elf *elf, int change_bo, size_t shnum)
 	  (*fctp) ((char *) elf->map_address + elf->start_offset, ehdr,
 		   sizeof (ElfW2(LIBELFBITS,Ehdr)), 1);
 	}
-      else
+      else if (elf->map_address + elf->start_offset != ehdr)
 	memcpy (elf->map_address + elf->start_offset, ehdr,
 		sizeof (ElfW2(LIBELFBITS,Ehdr)));
 
-- 
1.7.1



More information about the elfutils-devel mailing list