On Wed, Jun 12, 2024 at 04:57:09PM +0100, Mate Kukri wrote:
> 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 <pjo...@redhat.com>
> Original-Author: Robbie Harwood <rharw...@redhat.com>
> Original-Author: Laszlo Ersek <ler...@redhat.com>
> Signed-off-by: Mate Kukri <mate.ku...@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 8338f7436..3341d78d6 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;
This hunk is suspicious...
> - 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;
s/unsigned/unsigned int/
> + 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;
Wrong coding style for function calls and casts.
> + 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)
Wrong casts coding style...
> + 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);
Missing space before and after "|" (I saw similar mistakes in the other
places too). And you do not need to wrap this line.
> + 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 8a37cc16f..84a249834 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
>
> /*
> @@ -254,6 +255,51 @@ grub_dl_is_persistent (grub_dl_t mod)
> return mod->persistent;
> }
>
> +#pragma GCC diagnostic ignored "-Wcast-align"
Why? Please add a comment before pragma. And this suggests you should
probably use grub_unaligned_*() instead.
> +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/unsigned/long/ and then you do not need cast below...
> +
> + 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;
s/(long)i/(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;
> +}
I think you should restore "-Wcast-align" here. If it is really needed...
Daniel
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