On Wed, 27 Jan 2016 17:29:37 +0100 Piotr Kwapulinski <kwapulinski.piotr@xxxxxxxxx> 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@xxxxxxxxxxxxxxx>
AuthorDate: Fri Feb 12 13:02:40 2016 -0800
Commit: Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxx>
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@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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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