Merge tag 'efi-urgent-for-v5.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi into efi/urgent

Pull EFI fixes from Ard Biesheuvel:

 A batch of fixes for the arm64 stub image loader:

 - fix a logic bug that can make the random page allocator fail
   spuriously
 - force reallocation of the Image when it overlaps with firmware
   reserved memory regions
 - fix an oversight that defeated on optimization introduced earlier
   where images loaded at a suitable offset are never moved if booting
   without randomization
 - complain about images that were not loaded at the right offset by the
   firmware image loader.

Link: https://lore.kernel.org/r/20210803091215.2566-1-ardb@kernel.org

2 files changed, 63 insertions, 10 deletions

diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index 7bf0a7acae5e..2363fee9211c 100644
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -35,15 +35,48 @@ efi_status_t check_platform_features(void)
 }
 
 /*
- * Although relocatable kernels can fix up the misalignment with respect to
- * MIN_KIMG_ALIGN, the resulting virtual text addresses are subtly out of
- * sync with those recorded in the vmlinux when kaslr is disabled but the
- * image required relocation anyway. Therefore retain 2M alignment unless
- * KASLR is in use.
+ * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
+ * to provide space, and fail to zero it). Check for this condition by double
+ * checking that the first and the last byte of the image are covered by the
+ * same EFI memory map entry.
  */
-static u64 min_kimg_align(void)
+static bool check_image_region(u64 base, u64 size)
 {
-	return efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
+	unsigned long map_size, desc_size, buff_size;
+	efi_memory_desc_t *memory_map;
+	struct efi_boot_memmap map;
+	efi_status_t status;
+	bool ret = false;
+	int map_offset;
+
+	map.map =	&memory_map;
+	map.map_size =	&map_size;
+	map.desc_size =	&desc_size;
+	map.desc_ver =	NULL;
+	map.key_ptr =	NULL;
+	map.buff_size =	&buff_size;
+
+	status = efi_get_memory_map(&map);
+	if (status != EFI_SUCCESS)
+		return false;
+
+	for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
+		efi_memory_desc_t *md = (void *)memory_map + map_offset;
+		u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
+
+		/*
+		 * Find the region that covers base, and return whether
+		 * it covers base+size bytes.
+		 */
+		if (base >= md->phys_addr && base < end) {
+			ret = (base + size) <= end;
+			break;
+		}
+	}
+
+	efi_bs_call(free_pool, memory_map);
+
+	return ret;
 }
 
 efi_status_t handle_kernel_image(unsigned long *image_addr,
@@ -56,6 +89,16 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 	unsigned long kernel_size, kernel_memsize = 0;
 	u32 phys_seed = 0;
 
+	/*
+	 * Although relocatable kernels can fix up the misalignment with
+	 * respect to MIN_KIMG_ALIGN, the resulting virtual text addresses are
+	 * subtly out of sync with those recorded in the vmlinux when kaslr is
+	 * disabled but the image required relocation anyway. Therefore retain
+	 * 2M alignment if KASLR was explicitly disabled, even if it was not
+	 * going to be activated to begin with.
+	 */
+	u64 min_kimg_align = efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
+
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
 		if (!efi_nokaslr) {
 			status = efi_get_random_bytes(sizeof(phys_seed),
@@ -76,6 +119,10 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 	if (image->image_base != _text)
 		efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
 
+	if (!IS_ALIGNED((u64)_text, EFI_KIMG_ALIGN))
+		efi_err("FIRMWARE BUG: kernel image not aligned on %ldk boundary\n",
+			EFI_KIMG_ALIGN >> 10);
+
 	kernel_size = _edata - _text;
 	kernel_memsize = kernel_size + (_end - _edata);
 	*reserve_size = kernel_memsize;
@@ -85,14 +132,18 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 		 * If KASLR is enabled, and we have some randomness available,
 		 * locate the kernel at a randomized offset in physical memory.
 		 */
-		status = efi_random_alloc(*reserve_size, min_kimg_align(),
+		status = efi_random_alloc(*reserve_size, min_kimg_align,
 					  reserve_addr, phys_seed);
+		if (status != EFI_SUCCESS)
+			efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
 	} else {
 		status = EFI_OUT_OF_RESOURCES;
 	}
 
 	if (status != EFI_SUCCESS) {
-		if (IS_ALIGNED((u64)_text, min_kimg_align())) {
+		if (!check_image_region((u64)_text, kernel_memsize)) {
+			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
+		} else if (IS_ALIGNED((u64)_text, min_kimg_align)) {
 			/*
 			 * Just execute from wherever we were loaded by the
 			 * UEFI PE/COFF loader if the alignment is suitable.
@@ -103,7 +154,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
 		}
 
 		status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
-						    ULONG_MAX, min_kimg_align());
+						    ULONG_MAX, min_kimg_align);
 
 		if (status != EFI_SUCCESS) {
 			efi_err("Failed to relocate kernel\n");
diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
index a408df474d83..724155b9e10d 100644
--- a/drivers/firmware/efi/libstub/randomalloc.c
+++ b/drivers/firmware/efi/libstub/randomalloc.c
@@ -30,6 +30,8 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
 
 	region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
 			 (u64)ULONG_MAX);
+	if (region_end < size)
+		return 0;
 
 	first_slot = round_up(md->phys_addr, align);
 	last_slot = round_down(region_end - size + 1, align);