Messages in this thread Patch in this message | | | Date | Fri, 26 Feb 2016 12:20:32 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v2] mm/mprotect.c: don't imply PROT_EXEC on non-exec fs |
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On Wed, 27 Jan 2016 17:29:37 +0100 Piotr Kwapulinski <kwapulinski.piotr@gmail.com> 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 <dave.hansen@linux.intel.com> AuthorDate: Fri Feb 12 13:02:40 2016 -0800 Commit: Ingo Molnar <mingo@kernel.org> 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 <kwapulinski.piotr@gmail.com> 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 <kwapulinski.piotr@gmail.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
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); _
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