Commit 2d4cf7b1 authored by Kees Cook's avatar Kees Cook
Browse files

binfmt_elf: Calculate total_size earlier 

In preparation to support PT_LOAD with large p_align values on
non-PT_INTERP ET_DYN executables (i.e. "static pie"), we'll need to use
the total_size details earlier. Move this separately now to make the
next patch more readable. As total_size and load_bias are currently
calculated separately, this has no behavioral impact.

Link: https://lore.kernel.org/r/20240508173149.677910-2-keescook@chromium.org


Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent b57a2907

fs/binfmt_elf.c

+27 −25
Original line number Diff line number Diff line
@@ -1061,7 +1061,34 @@ static int load_elf_binary(struct linux_binprm *bprm) 
			 * Header for ET_DYN binaries to calculate the

			 * randomization (load_bias) for all the LOAD

			 * Program Headers.

			 */



			/*

			 * Calculate the entire size of the ELF mapping

			 * (total_size), used for the initial mapping,

			 * due to load_addr_set which is set to true later

			 * once the initial mapping is performed.

			 *

			 * Note that this is only sensible when the LOAD

			 * segments are contiguous (or overlapping). If

			 * used for LOADs that are far apart, this would

			 * cause the holes between LOADs to be mapped,

			 * running the risk of having the mapping fail,

			 * as it would be larger than the ELF file itself.

			 *

			 * As a result, only ET_DYN does this, since

			 * some ET_EXEC (e.g. ia64) may have large virtual

			 * memory holes between LOADs.

			 *

			 */

			total_size = total_mapping_size(elf_phdata,

							elf_ex->e_phnum);

			if (!total_size) {

				retval = -EINVAL;

				goto out_free_dentry;

			}



			/*

			 * There are effectively two types of ET_DYN

			 * binaries: programs (i.e. PIE: ET_DYN with INTERP)

			 * and loaders (ET_DYN without INTERP, since they
@@ -1102,31 +1129,6 @@ static int load_elf_binary(struct linux_binprm *bprm) 
			 * is then page aligned.

			 */

			load_bias = ELF_PAGESTART(load_bias - vaddr);



			/*

			 * Calculate the entire size of the ELF mapping

			 * (total_size), used for the initial mapping,

			 * due to load_addr_set which is set to true later

			 * once the initial mapping is performed.

			 *

			 * Note that this is only sensible when the LOAD

			 * segments are contiguous (or overlapping). If

			 * used for LOADs that are far apart, this would

			 * cause the holes between LOADs to be mapped,

			 * running the risk of having the mapping fail,

			 * as it would be larger than the ELF file itself.

			 *

			 * As a result, only ET_DYN does this, since

			 * some ET_EXEC (e.g. ia64) may have large virtual

			 * memory holes between LOADs.

			 *

			 */

			total_size = total_mapping_size(elf_phdata,

							elf_ex->e_phnum);

			if (!total_size) {

				retval = -EINVAL;

				goto out_free_dentry;

			}

		}



		error = elf_load(bprm->file, load_bias + vaddr, elf_ppnt,