2005-09-09 Roland McGrath <roland@redhat.com>
* elf_update.c (write_file): Stat the file and fchmod it after update
if its mode had S_ISUID or S_ISGID bits set.
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index bd710ae..35667ce 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2005-09-09 Roland McGrath <roland@redhat.com>
+
+ * elf_update.c (write_file): Stat the file and fchmod it after update
+ if its mode had S_ISUID or S_ISGID bits set.
+
2005-08-28 Ulrich Drepper <drepper@redhat.com>
* elf32_getphdr.c: Include <system.h>. Use pread_retry instead of
diff --git a/libelf/elf_update.c b/libelf/elf_update.c
index 5d6c6b7..f380e2b 100644
--- a/libelf/elf_update.c
+++ b/libelf/elf_update.c
@@ -22,6 +22,7 @@
#include <libelf.h>
#include <unistd.h>
#include <sys/mman.h>
+#include <sys/stat.h>
#include "libelfP.h"
@@ -31,6 +32,14 @@
{
int class = elf->class;
+ /* Check the mode bits now, before modification might change them. */
+ struct stat st;
+ if (unlikely (fstat (elf->fildes, &st) != 0))
+ {
+ __libelf_seterrno (ELF_E_WRITE_ERROR);
+ return -1;
+ }
+
/* Adjust the size in any case. We do this even if we use `write'.
We cannot do this if this file is in an archive. We also don't
do it *now* if we are shortening the file since this would
@@ -87,6 +96,18 @@
size = -1;
}
+ /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
+ mode bits. So make sure we restore them afterwards if they were set.
+ This is not atomic if someone else chmod's the file while we operate. */
+ if (size != -1
+ && unlikely (st.st_mode & (S_ISUID | S_ISGID))
+ /* fchmod ignores the bits we cannot change. */
+ && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
+ {
+ __libelf_seterrno (ELF_E_WRITE_ERROR);
+ size = -1;
+ }
+
if (size != -1 && elf->parent == NULL)
elf->maximum_size = size;