File 0006-nx-set-page-permissions-for-loaded-modules.patch of Package grub2
From a5bc33b962c34f72f60a6764cdd7feecdc59c384 Mon Sep 17 00:00:00 2001
From: Mate Kukri <mate.kukri@canonical.com>
Date: Wed, 12 Jun 2024 16:57:09 +0100
Subject: [PATCH 06/10] nx: set page permissions for loaded modules.
For NX, we need to set write and executable permissions on the sections
of grub modules when we load them.
On sections with SHF_ALLOC set, which is typically everything except
.modname and the symbol and string tables, this patch clears the Read
Only flag on sections that have the ELF flag SHF_WRITE set, and clears
the No eXecute flag on sections with SHF_EXECINSTR set. In all other
cases it sets both flags.
Original-Author: Peter Jones <pjones@redhat.com>
Original-Author: Robbie Harwood <rharwood@redhat.com>
Original-Author: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Mate Kukri <mate.kukri@canonical.com>
---
grub-core/kern/dl.c | 104 ++++++++++++++++++++++++++++++++++++++------
include/grub/dl.h | 46 ++++++++++++++++++++
2 files changed, 137 insertions(+), 13 deletions(-)
diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
index 3cf711a1b..77699cb07 100644
--- a/grub-core/kern/dl.c
+++ b/grub-core/kern/dl.c
@@ -616,25 +616,97 @@ grub_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
grub_dl_segment_t seg;
grub_err_t err;
- /* Find the target segment. */
- for (seg = mod->segment; seg; seg = seg->next)
- if (seg->section == s->sh_info)
- break;
+ seg = grub_dl_find_segment(mod, s->sh_info);
+ if (!seg)
+ continue;
- if (seg)
- {
- if (!mod->symtab)
- return grub_error (GRUB_ERR_BAD_MODULE, "relocation without symbol table");
+ if (!mod->symtab)
+ return grub_error (GRUB_ERR_BAD_MODULE, "relocation without symbol table");
- err = grub_arch_dl_relocate_symbols (mod, ehdr, s, seg);
- if (err)
- return err;
- }
+ err = grub_arch_dl_relocate_symbols (mod, ehdr, s, seg);
+ if (err)
+ return err;
}
return GRUB_ERR_NONE;
}
+/* Only define this on EFI to save space in core */
+#ifdef GRUB_MACHINE_EFI
+static grub_err_t
+grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr)
+{
+ unsigned i;
+ const Elf_Shdr *s;
+ const Elf_Ehdr *e = ehdr;
+ grub_err_t err;
+#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
+ grub_size_t arch_addralign = grub_arch_dl_min_alignment ();
+ grub_addr_t tgaddr;
+ grub_size_t tgsz;
+#endif
+
+ for (i = 0, s = (const Elf_Shdr *)((const char *) e + e->e_shoff);
+ i < e->e_shnum;
+ i++, s = (const Elf_Shdr *)((const char *) s + e->e_shentsize))
+ {
+ grub_dl_segment_t seg;
+ grub_uint64_t set_attrs = GRUB_MEM_ATTR_R;
+ grub_uint64_t clear_attrs = GRUB_MEM_ATTR_W|GRUB_MEM_ATTR_X;
+
+ seg = grub_dl_find_segment(mod, i);
+ if (!seg)
+ continue;
+
+ if (seg->size == 0 || !(s->sh_flags & SHF_ALLOC))
+ continue;
+
+ if (s->sh_flags & SHF_WRITE)
+ {
+ set_attrs |= GRUB_MEM_ATTR_W;
+ clear_attrs &= ~GRUB_MEM_ATTR_W;
+ }
+
+ if (s->sh_flags & SHF_EXECINSTR)
+ {
+ set_attrs |= GRUB_MEM_ATTR_X;
+ clear_attrs &= ~GRUB_MEM_ATTR_X;
+ }
+
+ err = grub_update_mem_attrs ((grub_addr_t)(seg->addr), seg->size,
+ set_attrs, clear_attrs);
+ if (err != GRUB_ERR_NONE)
+ return err;
+ }
+
+#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
+ tgaddr = grub_min((grub_addr_t)mod->tramp, (grub_addr_t)mod->got);
+ tgsz = grub_max((grub_addr_t)mod->trampptr, (grub_addr_t)mod->gotptr) - tgaddr;
+
+ if (tgsz)
+ {
+ tgsz = ALIGN_UP(tgsz, arch_addralign);
+
+ if (tgaddr < (grub_addr_t)mod->base ||
+ tgsz > (grub_addr_t)-1 - tgaddr ||
+ tgaddr + tgsz > (grub_addr_t)mod->base + mod->sz)
+ return grub_error (GRUB_ERR_BUG,
+ "BUG: trying to protect pages outside of module "
+ "allocation (\"%s\"): module base %p, size 0x%"
+ PRIxGRUB_SIZE "; tramp/GOT base 0x%" PRIxGRUB_ADDR
+ ", size 0x%" PRIxGRUB_SIZE,
+ mod->name, mod->base, mod->sz, tgaddr, tgsz);
+ err = grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X,
+ GRUB_MEM_ATTR_W);
+ if (err != GRUB_ERR_NONE)
+ return err;
+ }
+#endif
+
+ return GRUB_ERR_NONE;
+}
+#endif
+
/* Load a module from core memory. */
grub_dl_t
grub_dl_load_core_noinit (void *addr, grub_size_t size)
@@ -668,6 +740,7 @@ grub_dl_load_core_noinit (void *addr, grub_size_t size)
mod->ref_count = 1;
grub_dprintf ("modules", "relocating to %p\n", mod);
+
/* Me, Vladimir Serbinenko, hereby I add this module check as per new
GNU module policy. Note that this license check is informative only.
Modules have to be licensed under GPLv3 or GPLv3+ (optionally
@@ -681,7 +754,12 @@ grub_dl_load_core_noinit (void *addr, grub_size_t size)
|| grub_dl_resolve_dependencies (mod, e)
|| grub_dl_load_segments (mod, e)
|| grub_dl_resolve_symbols (mod, e)
- || grub_dl_relocate_symbols (mod, e))
+ || grub_dl_relocate_symbols (mod, e)
+#ifdef GRUB_MACHINE_EFI
+ || grub_dl_set_mem_attrs (mod, e))
+#else
+ )
+#endif
{
mod->fini = 0;
grub_dl_unload (mod);
diff --git a/include/grub/dl.h b/include/grub/dl.h
index 5eecf4e48..2e1f66451 100644
--- a/include/grub/dl.h
+++ b/include/grub/dl.h
@@ -27,6 +27,7 @@
#include <grub/elf.h>
#include <grub/list.h>
#include <grub/misc.h>
+#include <grub/mm.h>
#endif
/*
@@ -265,6 +266,51 @@ grub_dl_is_persistent (grub_dl_t mod)
return mod->persistent;
}
+#pragma GCC diagnostic ignored "-Wcast-align"
+
+static inline const char *
+grub_dl_get_section_name (const Elf_Ehdr *e, const Elf_Shdr *s)
+{
+ Elf_Shdr *str_s;
+ const char *str;
+
+ str_s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
+ str = (char *) e + str_s->sh_offset;
+
+ return str + s->sh_name;
+}
+
+static inline long
+grub_dl_find_section_index (Elf_Ehdr *e, const char *name)
+{
+ Elf_Shdr *s;
+ const char *str;
+ unsigned i;
+
+ s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
+ str = (char *) e + s->sh_offset;
+
+ for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
+ i < e->e_shnum;
+ i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
+ if (grub_strcmp (str + s->sh_name, name) == 0)
+ return (long)i;
+ return -1;
+}
+
+/* Return the segment for a section of index N */
+static inline grub_dl_segment_t
+grub_dl_find_segment (grub_dl_t mod, unsigned n)
+{
+ grub_dl_segment_t seg;
+
+ for (seg = mod->segment; seg; seg = seg->next)
+ if (seg->section == n)
+ return seg;
+
+ return NULL;
+}
+
#endif
grub_err_t grub_dl_register_symbol (const char *name, void *addr,
--
2.45.2
