[PATCH] Hardening memory maunipulation.

[PATCH] Hardening memory maunipulation.

[Shawn Chang]

From: Shawn C <citypw@gmail.com>

Hi kernel maintainers,

It won't allow the address above the TASK_SIZE being mmap'ed( or mprotect'ed).
This patch is from PaX/Grsecurity.

Thanks for your review time!

Signed-off-by: Shawn C <citypw@gmail.com>
---
 mm/madvise.c   | 4 ++++
 mm/mempolicy.c | 5 +++++
 mm/mlock.c     | 4 ++++
 mm/mprotect.c  | 5 +++++
 4 files changed, 18 insertions(+)

diff --git a/mm/madvise.c b/mm/madvise.c
index d551475..3f5dd3d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -484,6 +484,10 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 	if (end < start)
 		return error;
 
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return error;
+
 	error = 0;
 	if (end == start)
 		return error;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index ede2629..56c2eed 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1161,6 +1161,11 @@ static long do_mbind(unsigned long start, unsigned long len,
 
 	if (end < start)
 		return -EINVAL;
+
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	if (end == start)
 		return 0;
 
diff --git a/mm/mlock.c b/mm/mlock.c
index 6fd2cf1..c7f6785 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -566,6 +566,10 @@ static int do_mlock(unsigned long start, size_t len, int on)
 		return -EINVAL;
 	if (end == start)
 		return 0;
+
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	vma = find_vma(current->mm, start);
 	if (!vma || vma->vm_start > start)
 		return -ENOMEM;
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 8858483..cd58a31 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -351,6 +351,11 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 	end = start + len;
 	if (end <= start)
 		return -ENOMEM;
+
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	if (!arch_validate_prot(prot))
 		return -EINVAL;
 
-- 
1.9.1

[PATCH] Hardening memory maunipulation.

[Shawn Chang]

From: Shawn C <citypw@gmail.com>

Hi kernel maintainers,

It won't allow the address above the TASK_SIZE being mmap'ed( or mprotect'ed).
This patch is from PaX/Grsecurity.

Thanks for your review time!

Signed-off-by: Shawn C <citypw@gmail.com>
---
 mm/madvise.c   | 4 ++++
 mm/mempolicy.c | 5 +++++
 mm/mlock.c     | 4 ++++
 mm/mprotect.c  | 5 +++++
 4 files changed, 18 insertions(+)

diff --git a/mm/madvise.c b/mm/madvise.c
index d551475..3f5dd3d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -484,6 +484,10 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 	if (end < start)
 		return error;
 
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return error;
+
 	error = 0;
 	if (end == start)
 		return error;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index ede2629..56c2eed 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1161,6 +1161,11 @@ static long do_mbind(unsigned long start, unsigned long len,
 
 	if (end < start)
 		return -EINVAL;
+
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	if (end == start)
 		return 0;
 
diff --git a/mm/mlock.c b/mm/mlock.c
index 6fd2cf1..c7f6785 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -566,6 +566,10 @@ static int do_mlock(unsigned long start, size_t len, int on)
 		return -EINVAL;
 	if (end == start)
 		return 0;
+
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	vma = find_vma(current->mm, start);
 	if (!vma || vma->vm_start > start)
 		return -ENOMEM;
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 8858483..cd58a31 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -351,6 +351,11 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
 	end = start + len;
 	if (end <= start)
 		return -ENOMEM;
+
+	/* We should never reach the kernel address space here */
+	if (end > TASK_SIZE)
+		return -EINVAL;
+
 	if (!arch_validate_prot(prot))
 		return -EINVAL;
 
-- 
1.9.1

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Re: [PATCH] Hardening memory maunipulation.

[Andy Lutomirski]

On 04/29/2015 08:39 AM, Shawn Chang wrote:
> From: Shawn C <citypw@gmail.com>
>
> Hi kernel maintainers,
>
> It won't allow the address above the TASK_SIZE being mmap'ed( or mprotect'ed).
> This patch is from PaX/Grsecurity.
>
> Thanks for your review time!

Does this actually reduce the attack surface of anything?

These functions all search for vmas.  If there's a vma outside of the 
user range, we have a problem.

Also, that use of TASK_SIZE is IMO ridiculous.  Shouldn't be TASK_SIZE_MAX?

--Andy, who is annoyed every time another pointless TIF_IA32 reference, 
even hidden in a macro, makes it into the kernel

Re: [PATCH] Hardening memory maunipulation.

[Andy Lutomirski]

On 04/29/2015 08:39 AM, Shawn Chang wrote:
> From: Shawn C <citypw@gmail.com>
>
> Hi kernel maintainers,
>
> It won't allow the address above the TASK_SIZE being mmap'ed( or mprotect'ed).
> This patch is from PaX/Grsecurity.
>
> Thanks for your review time!

Does this actually reduce the attack surface of anything?

These functions all search for vmas.  If there's a vma outside of the 
user range, we have a problem.

Also, that use of TASK_SIZE is IMO ridiculous.  Shouldn't be TASK_SIZE_MAX?

--Andy, who is annoyed every time another pointless TIF_IA32 reference, 
even hidden in a macro, makes it into the kernel

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see: http://www.linux-mm.org/ .
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