[PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Oleg Nesterov]

uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
some architectures (csky, s390, and sparc) don't do this.

We can remove the BUG_ON() check in prepare_uprobe() and validate the
offset early in __uprobe_register(). The new IS_ALIGNED() check matches
the alignment check in arch_prepare_kprobe() on supported architectures,
so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.

Another problem is __update_ref_ctr() which was wrong from the very
beginning, it can read/write outside of kmap'ed page unless "vaddr" is
aligned to sizeof(short), __uprobe_register() should check this too.

Cc: stable@vger.kernel.org
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/events/uprobes.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index ece7e13f6e4a..cc2095607c74 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -867,10 +867,6 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
 	if (ret)
 		goto out;
 
-	/* uprobe_write_opcode() assumes we don't cross page boundary */
-	BUG_ON((uprobe->offset & ~PAGE_MASK) +
-			UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
-
 	smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
 	set_bit(UPROBE_COPY_INSN, &uprobe->flags);
 
@@ -1166,6 +1162,15 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 	if (offset > i_size_read(inode))
 		return -EINVAL;
 
+	/*
+	 * This ensures that copy_from_page(), copy_to_page() and
+	 * __update_ref_ctr() can't cross page boundary.
+	 */
+	if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
+		return -EINVAL;
+	if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
+		return -EINVAL;
+
  retry:
 	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
 	if (!uprobe)
@@ -2014,6 +2019,9 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
 	uprobe_opcode_t opcode;
 	int result;
 
+	if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE)))
+		return -EINVAL;
+
 	pagefault_disable();
 	result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
 	pagefault_enable();
-- 
2.25.1.362.g51ebf55

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Christian Borntraeger]

On 04.05.20 18:47, Oleg Nesterov wrote:
> uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> some architectures (csky, s390, and sparc) don't do this.

I think the idea was that the uprobe instruction is 2 bytes and instructions
are always aligned to 2 bytes on s390.  (we can have 2,4 or 6 bytes).

> 
> We can remove the BUG_ON() check in prepare_uprobe() and validate the
> offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> the alignment check in arch_prepare_kprobe() on supported architectures,
> so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.

Not sure if it would have been possible to try to create a uprobe on an 
odd address. If yes, then the new IS_ALIGNED check certainly makes this
better for s390, so the patch looks sane. Adding Vasily and Sven to double
check.


> 
> Another problem is __update_ref_ctr() which was wrong from the very
> beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> aligned to sizeof(short), __uprobe_register() should check this too.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>  kernel/events/uprobes.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index ece7e13f6e4a..cc2095607c74 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -867,10 +867,6 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
>  	if (ret)
>  		goto out;
>  
> -	/* uprobe_write_opcode() assumes we don't cross page boundary */
> -	BUG_ON((uprobe->offset & ~PAGE_MASK) +
> -			UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
> -
>  	smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
>  	set_bit(UPROBE_COPY_INSN, &uprobe->flags);
>  
> @@ -1166,6 +1162,15 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
>  	if (offset > i_size_read(inode))
>  		return -EINVAL;
>  
> +	/*
> +	 * This ensures that copy_from_page(), copy_to_page() and
> +	 * __update_ref_ctr() can't cross page boundary.
> +	 */
> +	if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
> +		return -EINVAL;
> +	if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
> +		return -EINVAL;
> +
>   retry:
>  	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
>  	if (!uprobe)
> @@ -2014,6 +2019,9 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
>  	uprobe_opcode_t opcode;
>  	int result;
>  
> +	if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE)))
> +		return -EINVAL;
> +
>  	pagefault_disable();
>  	result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
>  	pagefault_enable();
> 

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Sven Schnelle]

Hi,

On Mon, May 04, 2020 at 08:40:44PM +0200, Christian Borntraeger wrote:
> 
> 
> On 04.05.20 18:47, Oleg Nesterov wrote:
> > uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> > some architectures (csky, s390, and sparc) don't do this.
> 
> I think the idea was that the uprobe instruction is 2 bytes and instructions
> are always aligned to 2 bytes on s390.  (we can have 2,4 or 6 bytes).
> 
> > 
> > We can remove the BUG_ON() check in prepare_uprobe() and validate the
> > offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> > the alignment check in arch_prepare_kprobe() on supported architectures,
> > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
> 
> Not sure if it would have been possible to try to create a uprobe on an 
> odd address. If yes, then the new IS_ALIGNED check certainly makes this
> better for s390, so the patch looks sane. Adding Vasily and Sven to double
> check.

I did a quick test, and without this patch it is possible to place a uprobe
at an odd address. With the patch it fails with EINVAL, which is more
reasonable.

Regards
Sven

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Guo Ren]

On Tue, May 5, 2020 at 2:41 AM Christian Borntraeger
<borntraeger@de.ibm.com> wrote:
>
>
>
> On 04.05.20 18:47, Oleg Nesterov wrote:
> > uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> > some architectures (csky, s390, and sparc) don't do this.
>
> I think the idea was that the uprobe instruction is 2 bytes and instructions
> are always aligned to 2 bytes on s390.  (we can have 2,4 or 6 bytes).
Agree, csky has two length-types of instructions (2,4 bytes).

>
> >
> > We can remove the BUG_ON() check in prepare_uprobe() and validate the
> > offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> > the alignment check in arch_prepare_kprobe() on supported architectures,
> > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
>
> Not sure if it would have been possible to try to create a uprobe on an
> odd address. If yes, then the new IS_ALIGNED check certainly makes this
> better for s390, so the patch looks sane. Adding Vasily and Sven to double
> check.
Also good to csky.

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Srikar Dronamraju]

* Oleg Nesterov <oleg@redhat.com> [2020-05-04 18:47:25]:

> uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> some architectures (csky, s390, and sparc) don't do this.
> 
> We can remove the BUG_ON() check in prepare_uprobe() and validate the
> offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> the alignment check in arch_prepare_kprobe() on supported architectures,
> so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
> 
> Another problem is __update_ref_ctr() which was wrong from the very
> beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> aligned to sizeof(short), __uprobe_register() should check this too.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Thanks Oleg.

Looks good to me.

Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---


-- 
Thanks and Regards
Srikar Dronamraju

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Steven Rostedt]

On Wed, 6 May 2020 10:59:55 +0530
Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:

> * Oleg Nesterov <oleg@redhat.com> [2020-05-04 18:47:25]:
> 
> > uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> > some architectures (csky, s390, and sparc) don't do this.
> > 
> > We can remove the BUG_ON() check in prepare_uprobe() and validate the
> > offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> > the alignment check in arch_prepare_kprobe() on supported architectures,
> > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
> > 
> > Another problem is __update_ref_ctr() which was wrong from the very
> > beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> > aligned to sizeof(short), __uprobe_register() should check this too.
> > 
> > Cc: stable@vger.kernel.org
> > Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Oleg Nesterov <oleg@redhat.com>  
> 
> Thanks Oleg.
> 
> Looks good to me.
> 
> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> > ---  
> 

Thanks Oleg, Srikar and Sven.

As this is in the kernel/events/ directory, I'm guessing it should be taken
through the tip tree?

-- Steve

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Oleg Nesterov]

On 05/06, Steven Rostedt wrote:
>
> As this is in the kernel/events/ directory, I'm guessing it should be taken
> through the tip tree?

this would be great, thanks Steven.

Oleg.

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Oleg Nesterov]

Looks like this patch was forgotten...

Should I resend it?

On 05/04, Oleg Nesterov wrote:
>
> uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> some architectures (csky, s390, and sparc) don't do this.
> 
> We can remove the BUG_ON() check in prepare_uprobe() and validate the
> offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> the alignment check in arch_prepare_kprobe() on supported architectures,
> so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
> 
> Another problem is __update_ref_ctr() which was wrong from the very
> beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> aligned to sizeof(short), __uprobe_register() should check this too.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>  kernel/events/uprobes.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index ece7e13f6e4a..cc2095607c74 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -867,10 +867,6 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
>  	if (ret)
>  		goto out;
>  
> -	/* uprobe_write_opcode() assumes we don't cross page boundary */
> -	BUG_ON((uprobe->offset & ~PAGE_MASK) +
> -			UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
> -
>  	smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
>  	set_bit(UPROBE_COPY_INSN, &uprobe->flags);
>  
> @@ -1166,6 +1162,15 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
>  	if (offset > i_size_read(inode))
>  		return -EINVAL;
>  
> +	/*
> +	 * This ensures that copy_from_page(), copy_to_page() and
> +	 * __update_ref_ctr() can't cross page boundary.
> +	 */
> +	if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
> +		return -EINVAL;
> +	if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
> +		return -EINVAL;
> +
>   retry:
>  	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
>  	if (!uprobe)
> @@ -2014,6 +2019,9 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
>  	uprobe_opcode_t opcode;
>  	int result;
>  
> +	if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE)))
> +		return -EINVAL;
> +
>  	pagefault_disable();
>  	result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
>  	pagefault_enable();
> -- 
> 2.25.1.362.g51ebf55
> 

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Linus Torvalds]

On Tue, Jun 9, 2020 at 8:30 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> Looks like this patch was forgotten...
>
> Should I resend it?

I guess I'll just take it directly, since it was triggered by me
complaining anyway.

I had hoped it would go through the usual channels.

                Linus

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Steven Rostedt]

On Tue, 9 Jun 2020 09:48:45 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Tue, Jun 9, 2020 at 8:30 AM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Looks like this patch was forgotten...
> >
> > Should I resend it?  
> 
> I guess I'll just take it directly, since it was triggered by me
> complaining anyway.
> 
> I had hoped it would go through the usual channels.

Perhaps there was confusion about which tree it was suppose to go
through :-/

-- Steve

Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr_offset are properly aligned

[Guo Ren]

Hi Oleg,

On Tue, May 5, 2020 at 12:47 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> some architectures (csky, s390, and sparc) don't do this.
>
> We can remove the BUG_ON() check in prepare_uprobe() and validate the
> offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> the alignment check in arch_prepare_kprobe() on supported architectures,
> so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
>
> Another problem is __update_ref_ctr() which was wrong from the very
> beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> aligned to sizeof(short), __uprobe_register() should check this too.
>
> Cc: stable@vger.kernel.org
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>  kernel/events/uprobes.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index ece7e13f6e4a..cc2095607c74 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -867,10 +867,6 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
>         if (ret)
>                 goto out;
>
> -       /* uprobe_write_opcode() assumes we don't cross page boundary */
> -       BUG_ON((uprobe->offset & ~PAGE_MASK) +
> -                       UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
> -
>         smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */
>         set_bit(UPROBE_COPY_INSN, &uprobe->flags);
>
> @@ -1166,6 +1162,15 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
>         if (offset > i_size_read(inode))
>                 return -EINVAL;
>
> +       /*
> +        * This ensures that copy_from_page(), copy_to_page() and
> +        * __update_ref_ctr() can't cross page boundary.
> +        */
> +       if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
> +               return -EINVAL;
> +       if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
> +               return -EINVAL;
> +
>   retry:
>         uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
>         if (!uprobe)
> @@ -2014,6 +2019,9 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
>         uprobe_opcode_t opcode;
>         int result;
>
> +       if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE)))
> +               return -EINVAL;
> +
>         pagefault_disable();
>         result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr);
>         pagefault_enable();
> --
> 2.25.1.362.g51ebf55
>
>
Looks good to me, thx.

Reviewed-by: Guo Ren <guoren@kernel.org>

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/