binfmt_elf: Do not move brk for INTERP-less ET_EXEC

When brk was moved for binaries without an interpreter, it should have
been limited to ET_DYN only. In other words, the special case was an
ET_DYN that lacks an INTERP, not just an executable that lacks INTERP.
The bug manifested for giant static executables, where the brk would end
up in the middle of the text area on 32-bit architectures.

Reported-and-tested-by: Richard Kojedzinszky <richard@kojedz.in>
Fixes: bbdc6076d2e5 ("binfmt_elf: move brk out of mmap when doing direct loader exec")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index cec3b41..ad4c6b1 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1121,7 +1121,8 @@ out_free_interp:
                 * (since it grows up, and may collide early with the stack
                 * growing down), and into the unused ELF_ET_DYN_BASE region.
                 */
-               if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) && !interpreter)
+               if (IS_ENABLED(CONFIG_ARCH_HAS_ELF_RANDOMIZE) &&
+                   loc->elf_ex.e_type == ET_DYN && !interpreter)
                        current->mm->brk = current->mm->start_brk =
                                ELF_ET_DYN_BASE;