On Fri, Feb 26, 2016 at 12:20:32PM -0800, Andrew Morton wrote:
> On Wed, 27 Jan 2016 17:29:37 +0100 Piotr Kwapulinski
> <[email protected]> wrote:
>
> > The mprotect(PROT_READ) fails when called by the READ_IMPLIES_EXEC binary
> > on a memory mapped file located on non-exec fs. The mprotect does not
> > check whether fs is _executable_ or not. The PROT_EXEC flag is set
> > automatically even if a memory mapped file is located on non-exec fs.
> > Fix it by checking whether a memory mapped file is located on a non-exec
> > fs. If so the PROT_EXEC is not implied by the PROT_READ.
> > The implementation uses the VM_MAYEXEC flag set properly in mmap.
> > Now it is consistent with mmap.
> >
> > I did the isolated tests (PT_GNU_STACK X/NX, multiple VMAs, X/NX fs).
> > I also patched the official 3.19.0-47-generic Ubuntu 14.04 kernel
> > and it seems to work.
>
> sys_mprotect() just took a mangling in linux-next due to
>
> commit 62b5f7d013fc455b8db26cf01e421f4c0d264b92
> Author: Dave Hansen <[email protected]>
> AuthorDate: Fri Feb 12 13:02:40 2016 -0800
> Commit: Ingo Molnar <[email protected]>
> CommitDate: Thu Feb 18 19:46:33 2016 +0100
>
> mm/core, x86/mm/pkeys: Add execute-only protection keys support
>
>
> Here is my rework of your "mm/mprotect.c: don't imply PROT_EXEC on
> non-exec fs" to handle this. Please check very carefully.
>
>
> From: Piotr Kwapulinski <[email protected]>
> Subject: mm/mprotect.c: don't imply PROT_EXEC on non-exec fs
>
> The mprotect(PROT_READ) fails when called by the READ_IMPLIES_EXEC binary
> on a memory mapped file located on non-exec fs. The mprotect does not
> check whether fs is _executable_ or not. The PROT_EXEC flag is set
> automatically even if a memory mapped file is located on non-exec fs. Fix
> it by checking whether a memory mapped file is located on a non-exec fs.
> If so the PROT_EXEC is not implied by the PROT_READ. The implementation
> uses the VM_MAYEXEC flag set properly in mmap. Now it is consistent with
> mmap.
>
> I did the isolated tests (PT_GNU_STACK X/NX, multiple VMAs, X/NX fs). I
> also patched the official 3.19.0-47-generic Ubuntu 14.04 kernel and it
> seems to work.
>
> Signed-off-by: Piotr Kwapulinski <[email protected]>
> Cc: Mel Gorman <[email protected]>
> Cc: Kirill A. Shutemov <[email protected]>
> Cc: Aneesh Kumar K.V <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Konstantin Khlebnikov <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> ---
>
> mm/mprotect.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff -puN mm/mprotect.c~mm-mprotectc-dont-imply-prot_exec-on-non-exec-fs
> mm/mprotect.c
> --- a/mm/mprotect.c~mm-mprotectc-dont-imply-prot_exec-on-non-exec-fs
> +++ a/mm/mprotect.c
> @@ -359,6 +359,9 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
> struct vm_area_struct *vma, *prev;
> int error = -EINVAL;
> const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
> + const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
> + (prot & PROT_READ);
> +
> prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
> if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
> return -EINVAL;
> @@ -375,11 +378,6 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
> return -EINVAL;
>
> reqprot = prot;
> - /*
> - * Does the application expect PROT_READ to imply PROT_EXEC:
> - */
> - if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
> - prot |= PROT_EXEC;
>
> down_write(¤t->mm->mmap_sem);
>
> @@ -414,6 +412,10 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
>
> /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
>
> + /* Does the application expect PROT_READ to imply PROT_EXEC */
> + if (rier && (vma->vm_flags & VM_MAYEXEC))
> + prot |= PROT_EXEC;
> +
> newflags = calc_vm_prot_bits(prot, pkey);
> newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
>
> @@ -445,6 +447,7 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
> error = -ENOMEM;
> goto out;
> }
> + prot = reqprot;
> }
> out:
> up_write(¤t->mm->mmap_sem);
> _
>
It looks good. I also did some tests (non-MPK CPU) - passed.
Thank you.
