Messages in this thread Patch in this message | | | From | pageexec@freemail ... | Date | Thu, 10 Jul 2008 23:21:31 +0200 | Subject | Re: [Bug 11063][PATCH] exec: fix stack excutability without PT_GNU_STACK |
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On 10 Jul 2008 at 21:19, Hugh Dickins wrote:
> 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.
alternatively, if there's a concern of stack_vma->vm_flags manipulation during execve (maybe not now, but in the future or in non-ELF formats that also want to rely on personality bits), you could opt for a safer
vm_flags = vma->vm_flags | (VM_STACK_FLAGS & (VM_EXEC | VM_MAYEXEC));
to just recompute the exec rights related bits.
> Reported-by: pageexec@freemail.hu > Signed-off-by: Hugh Dickins <hugh@veritas.com> > Cc: stable@kernel.org > --- > > fs/exec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- 2.6.26-rc9/fs/exec.c 2008-06-21 08:41:19.000000000 +0100 > +++ linux/fs/exec.c 2008-07-10 20:02:25.000000000 +0100 > @@ -610,7 +610,7 @@ int setup_arg_pages(struct linux_binprm > bprm->exec -= stack_shift; > > down_write(&mm->mmap_sem); > - vm_flags = vma->vm_flags; > + vm_flags = VM_STACK_FLAGS; > > /* > * Adjust stack execute permissions; explicitly enable for >
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