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RE: Create a hook for inspecting program headers during library load
- From: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- To: Roland McGrath <roland at hack dot frob dot com>
- Cc: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, "Joseph Myers (joseph at codesourcery dot com)" <joseph at codesourcery dot com>
- Date: Thu, 2 Oct 2014 15:02:21 +0000
- Subject: RE: Create a hook for inspecting program headers during library load
- Authentication-results: sourceware.org; auth=none
- References: <6D39441BF12EF246A7ABCE6654B0235320F18A1B at LEMAIL01 dot le dot imgtec dot org> <20141001214949 dot 239022C3AAD at topped-with-meat dot com> <6D39441BF12EF246A7ABCE6654B0235320F18CA4 at LEMAIL01 dot le dot imgtec dot org> <20141001230906 dot 9B9852C3AAA at topped-with-meat dot com>
Patch updated below. Though I did remember Joseph steering me away from
an ifdef based interface while reworking this:
https://sourceware.org/ml/libc-alpha/2014-05/msg00045.html
Does this seem more appropriate?
Tested for x86_64-linux-gnu.
Thanks,
Matthew
* elf/dl-load.c (dl-load-stubs.h): Include.
(open_verify): Add hook for phdr check.
* elf/dl-load-stubs.h: New file.
---
elf/dl-load-stubs.h | 32 ++++++++++++++++++++++++++++++++
elf/dl-load.c | 6 ++++++
2 files changed, 38 insertions(+)
create mode 100644 elf/dl-load-stubs.h
diff --git a/elf/dl-load-stubs.h b/elf/dl-load-stubs.h
new file mode 100644
index 0000000..8eb671d
--- /dev/null
+++ b/elf/dl-load-stubs.h
@@ -0,0 +1,32 @@
+/* Stub implementations for loader functions.
+ Copyright (C) 2014 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* Provide a default implementation of elf_machine_reject_phdr_p if a port
+ has not provided its own. */
+
+#ifndef ELF_MACHINE_REJECT_PHDR_P
+/* Return true iff ELF program headers are incompatible with the running
+ host. */
+static inline bool
+elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, uint_fast16_t phnum,
+ const char *buf, size_t len, int fd,
+ struct link_map *map)
+{
+ return false;
+}
+#endif
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 016a99c..aff3506 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -31,6 +31,7 @@
#include <sys/stat.h>
#include <sys/types.h>
#include "dynamic-link.h"
+#include "dl-load-stubs.h"
#include <abi-tag.h>
#include <stackinfo.h>
#include <caller.h>
@@ -1697,6 +1698,11 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
}
}
+ if (__glibc_unlikely (
+ elf_machine_reject_phdr_p (phdr, ehdr->e_phnum, fbp->buf, fbp->len,
+ fd, loader)))
+ goto close_and_out;
+
/* Check .note.ABI-tag if present. */
for (ph = phdr; ph < &phdr[ehdr->e_phnum]; ++ph)
if (ph->p_type == PT_NOTE && ph->p_filesz >= 32 && ph->p_align >= 4)
--
1.9.4