From: Heinrich Schuchardt <[email protected]> When applying base relocations from a PE-COFF binary all data must be treated as untrusted. Add the following checks to efi_loader_relocate():
* Reject relocation blocks that don't start on a 32-bit aligned address. * Reject relocation blocks whose SizeOfBlock is smaller than the block header, which would cause an unsigned underflow when computing the entry count. * A block with SizeOfBlock == 0 is invalid and does not mark the end of the relocation table. * Reject relocation blocks that extend beyond the end of the relocation section. * Reject individual relocation entries whose target offset, together with the access width, exceeds the mapped image size, preventing out-of-bounds writes. Pass virt_size to efi_loader_relocate() from efi_load_pe() to enable the per-entry bounds check. Reported-by: Anas Cherni <[email protected]> Signed-off-by: Heinrich Schuchardt <[email protected]> --- v2: move rel->VirtualAddress > virt_size check out of inner loop --- lib/efi_loader/efi_image_loader.c | 85 +++++++++++++++++++++++++++---- 1 file changed, 74 insertions(+), 11 deletions(-) diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c index d002eb0c744..88400f9efa9 100644 --- a/lib/efi_loader/efi_image_loader.c +++ b/lib/efi_loader/efi_image_loader.c @@ -111,8 +111,9 @@ void efi_print_image_infos(void *pc) * Return: status code */ static efi_status_t efi_loader_relocate(const IMAGE_BASE_RELOCATION *rel, - unsigned long rel_size, void *efi_reloc, - unsigned long pref_address) + unsigned long rel_size, void *efi_reloc, + unsigned long pref_address, + unsigned long virt_size) { unsigned long delta = (unsigned long)efi_reloc - pref_address; const IMAGE_BASE_RELOCATION *end; @@ -122,34 +123,95 @@ static efi_status_t efi_loader_relocate(const IMAGE_BASE_RELOCATION *rel, return EFI_SUCCESS; end = (const IMAGE_BASE_RELOCATION *)((const char *)rel + rel_size); - while (rel + 1 < end && rel->SizeOfBlock) { + while (rel + 1 < end) { const uint16_t *relocs = (const uint16_t *)(rel + 1); + + /* Each block must start on a 32-bit boundary */ + if (!IS_ALIGNED((uintptr_t)rel, sizeof(uint32_t))) { + log_debug("Relocation block not 32-bit aligned\n"); + return EFI_LOAD_ERROR; + } + /* Relocation block cannot be shorter than its header */ + if (rel->SizeOfBlock < sizeof(*rel)) { + log_debug("Relocation block too small: %u\n", + rel->SizeOfBlock); + return EFI_LOAD_ERROR; + } + /* All relocation entries must be inside the .reloc section */ + if ((const char *)rel + rel->SizeOfBlock > (const char *)end) { + log_debug("Relocation block exceeds relocation data\n"); + return EFI_LOAD_ERROR; + } + /* + * Relocations must be within the virtual address range. + * This also ensures that there is no overflow in the + * entry_offset check below. + */ + if (rel->VirtualAddress > virt_size) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } + i = (rel->SizeOfBlock - sizeof(*rel)) / sizeof(uint16_t); while (i--) { - uint32_t offset = (uint32_t)(*relocs & 0xfff) + - rel->VirtualAddress; + uint32_t entry_offset = *relocs & 0xfff; + unsigned long offset; int type = *relocs >> EFI_PAGE_SHIFT; - uint64_t *x64 = efi_reloc + offset; - uint32_t *x32 = efi_reloc + offset; - uint16_t *x16 = efi_reloc + offset; + uint64_t *x64; + uint32_t *x32; + uint16_t *x16; + + /* + * Relocation address must be within virtual address + * range. + */ + if (entry_offset > virt_size - rel->VirtualAddress) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } + + offset = rel->VirtualAddress + entry_offset; + x64 = efi_reloc + offset; + x32 = efi_reloc + offset; + x16 = efi_reloc + offset; switch (type) { case IMAGE_REL_BASED_ABSOLUTE: break; case IMAGE_REL_BASED_HIGH: + if (sizeof(uint16_t) > virt_size - offset) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } *x16 += ((uint32_t)delta) >> 16; break; case IMAGE_REL_BASED_LOW: + if (sizeof(uint16_t) > virt_size - offset) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } *x16 += (uint16_t)delta; break; case IMAGE_REL_BASED_HIGHLOW: + if (sizeof(uint32_t) > virt_size - offset) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } *x32 += (uint32_t)delta; break; case IMAGE_REL_BASED_DIR64: + if (sizeof(uint64_t) > virt_size - offset) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } *x64 += (uint64_t)delta; break; #ifdef __riscv case IMAGE_REL_BASED_RISCV_HI20: + if (sizeof(uint32_t) > virt_size - offset) { + log_debug("relocation address out of bounds\n"); + return EFI_LOAD_ERROR; + } *x32 = ((*x32 & 0xfffff000) + (uint32_t)delta) | (*x32 & 0x00000fff); break; @@ -163,7 +225,7 @@ static efi_status_t efi_loader_relocate(const IMAGE_BASE_RELOCATION *rel, break; #endif default: - log_err("Unknown Relocation off %x type %x\n", + log_err("Unknown Relocation off %lx type %x\n", offset, type); return EFI_LOAD_ERROR; } @@ -970,8 +1032,9 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle, /* Run through relocations */ if (efi_loader_relocate(rel, rel_size, efi_reloc, - (unsigned long)image_base) != EFI_SUCCESS) { - efi_free_pages((uintptr_t) efi_reloc, + (unsigned long)image_base, + virt_size) != EFI_SUCCESS) { + efi_free_pages((uintptr_t)efi_reloc, (virt_size + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT); ret = EFI_LOAD_ERROR; goto err; -- 2.53.0
