Commit 96a8e13e authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

exec: fix stack excutability without PT_GNU_STACK

Kernel Bugzilla #11063 points out that on some architectures (e.g. x86_32)
exec'ing an ELF without a PT_GNU_STACK program header should default to an
executable stack; but this got broken by the unlimited argv feature because
stack vma is now created before the right personality has been established:
so breaking old binaries using nested function trampolines.

Therefore re-evaluate VM_STACK_FLAGS in setup_arg_pages, where stack
vm_flags used to be set, before the mprotect_fixup.  Checking through
our existing VM_flags, none would have changed since insert_vm_struct:
so this seems safer than finding a way through the personality labyrinth.

Reported-by: pageexec@freemail.hu
Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f8804d39
...@@ -610,7 +610,7 @@ int setup_arg_pages(struct linux_binprm *bprm, ...@@ -610,7 +610,7 @@ int setup_arg_pages(struct linux_binprm *bprm,
bprm->exec -= stack_shift; bprm->exec -= stack_shift;
down_write(&mm->mmap_sem); down_write(&mm->mmap_sem);
vm_flags = vma->vm_flags; vm_flags = VM_STACK_FLAGS;
/* /*
* Adjust stack execute permissions; explicitly enable for * Adjust stack execute permissions; explicitly enable for
......
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