fs: binfmt_elf_efpic: don't use missing interpreter's properties

[ Upstream commit 15fd1dc3dadb4268207fa6797e753541aca09a2a ]

Static FDPIC executable may get an executable stack even when it has
non-executable GNU_STACK segment. This happens when STACK segment has rw
permissions, but does not specify stack size. In that case FDPIC loader
uses permissions of the interpreter's stack, and for static executables
with no interpreter it results in choosing the arch-default permissions
for the stack.

Fix that by using the interpreter's properties only when the interpreter
is actually used.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/r/20240118150637.660461-1-jcmvbkbc@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 48bb1290ed2fd0ce7f2c4efb563484e2cce04751..88428de9d873ec3f4edcc641bd798f19017a2394 100644 (file)
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -320,7 +320,7 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
        else
                executable_stack = EXSTACK_DEFAULT;
 
-       if (stack_size == 0) {
+       if (stack_size == 0 && interp_params.flags & ELF_FDPIC_FLAG_PRESENT) {
                stack_size = interp_params.stack_size;
                if (interp_params.flags & ELF_FDPIC_FLAG_EXEC_STACK)
                        executable_stack = EXSTACK_ENABLE_X;