[PATCH] bpf: propagate __user annotations properly

[PATCH] bpf: propagate __user annotations properly

[Lukas Bulwahn]

__htab_map_lookup_and_delete_batch() stores a user pointer in the local
variable ubatch and uses that in copy_{from,to}_user(), but ubatch misses a
__user annotation.

So, sparse warns in the various assignments and uses of ubatch:

  kernel/bpf/hashtab.c:1415:24: warning: incorrect type in initializer
    (different address spaces)
  kernel/bpf/hashtab.c:1415:24:    expected void *ubatch
  kernel/bpf/hashtab.c:1415:24:    got void [noderef] __user *

  kernel/bpf/hashtab.c:1444:46: warning: incorrect type in argument 2
    (different address spaces)
  kernel/bpf/hashtab.c:1444:46:    expected void const [noderef] __user *from
  kernel/bpf/hashtab.c:1444:46:    got void *ubatch

  kernel/bpf/hashtab.c:1608:16: warning: incorrect type in assignment
    (different address spaces)
  kernel/bpf/hashtab.c:1608:16:    expected void *ubatch
  kernel/bpf/hashtab.c:1608:16:    got void [noderef] __user *

  kernel/bpf/hashtab.c:1609:26: warning: incorrect type in argument 1
    (different address spaces)
  kernel/bpf/hashtab.c:1609:26:    expected void [noderef] __user *to
  kernel/bpf/hashtab.c:1609:26:    got void *ubatch

Add the __user annotation to repair this chain of propagating __user
annotations in __htab_map_lookup_and_delete_batch().

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
---
applies cleanly on current master (v5.10-rc7) and next-20201204

BPF maintainers, please pick this minor non-urgent clean-up patch.

 kernel/bpf/hashtab.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index fe7a0733a63a..76c791def033 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1412,7 +1412,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	void *keys = NULL, *values = NULL, *value, *dst_key, *dst_val;
 	void __user *uvalues = u64_to_user_ptr(attr->batch.values);
 	void __user *ukeys = u64_to_user_ptr(attr->batch.keys);
-	void *ubatch = u64_to_user_ptr(attr->batch.in_batch);
+	void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
 	u32 batch, max_count, size, bucket_size;
 	struct htab_elem *node_to_free = NULL;
 	u64 elem_map_flags, map_flags;
-- 
2.17.1

Re: [PATCH] bpf: propagate __user annotations properly

[Yonghong Song]

On 12/7/20 4:37 AM, Lukas Bulwahn wrote:
> __htab_map_lookup_and_delete_batch() stores a user pointer in the local
> variable ubatch and uses that in copy_{from,to}_user(), but ubatch misses a
> __user annotation.
> 
> So, sparse warns in the various assignments and uses of ubatch:
> 
>    kernel/bpf/hashtab.c:1415:24: warning: incorrect type in initializer
>      (different address spaces)
>    kernel/bpf/hashtab.c:1415:24:    expected void *ubatch
>    kernel/bpf/hashtab.c:1415:24:    got void [noderef] __user *
> 
>    kernel/bpf/hashtab.c:1444:46: warning: incorrect type in argument 2
>      (different address spaces)
>    kernel/bpf/hashtab.c:1444:46:    expected void const [noderef] __user *from
>    kernel/bpf/hashtab.c:1444:46:    got void *ubatch
> 
>    kernel/bpf/hashtab.c:1608:16: warning: incorrect type in assignment
>      (different address spaces)
>    kernel/bpf/hashtab.c:1608:16:    expected void *ubatch
>    kernel/bpf/hashtab.c:1608:16:    got void [noderef] __user *
> 
>    kernel/bpf/hashtab.c:1609:26: warning: incorrect type in argument 1
>      (different address spaces)
>    kernel/bpf/hashtab.c:1609:26:    expected void [noderef] __user *to
>    kernel/bpf/hashtab.c:1609:26:    got void *ubatch
> 
> Add the __user annotation to repair this chain of propagating __user
> annotations in __htab_map_lookup_and_delete_batch().

Add fix tag?

Fixes: 057996380a42 ("bpf: Add batch ops to all htab bpf map")

> 
> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>

Thanks for the fix. LGTM. I guess either bpf or bpf-next tree is fine
since this is not a correctness issue.

Acked-by: Yonghong Song <yhs@fb.com>

Re: [PATCH] bpf: propagate __user annotations properly

[Lukas Bulwahn]

On Mon, Dec 7, 2020 at 5:12 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 12/7/20 4:37 AM, Lukas Bulwahn wrote:
> > __htab_map_lookup_and_delete_batch() stores a user pointer in the local
> > variable ubatch and uses that in copy_{from,to}_user(), but ubatch misses a
> > __user annotation.
> >
> > So, sparse warns in the various assignments and uses of ubatch:
> >
> >    kernel/bpf/hashtab.c:1415:24: warning: incorrect type in initializer
> >      (different address spaces)
> >    kernel/bpf/hashtab.c:1415:24:    expected void *ubatch
> >    kernel/bpf/hashtab.c:1415:24:    got void [noderef] __user *
> >
> >    kernel/bpf/hashtab.c:1444:46: warning: incorrect type in argument 2
> >      (different address spaces)
> >    kernel/bpf/hashtab.c:1444:46:    expected void const [noderef] __user *from
> >    kernel/bpf/hashtab.c:1444:46:    got void *ubatch
> >
> >    kernel/bpf/hashtab.c:1608:16: warning: incorrect type in assignment
> >      (different address spaces)
> >    kernel/bpf/hashtab.c:1608:16:    expected void *ubatch
> >    kernel/bpf/hashtab.c:1608:16:    got void [noderef] __user *
> >
> >    kernel/bpf/hashtab.c:1609:26: warning: incorrect type in argument 1
> >      (different address spaces)
> >    kernel/bpf/hashtab.c:1609:26:    expected void [noderef] __user *to
> >    kernel/bpf/hashtab.c:1609:26:    got void *ubatch
> >
> > Add the __user annotation to repair this chain of propagating __user
> > annotations in __htab_map_lookup_and_delete_batch().
>
> Add fix tag?
>
> Fixes: 057996380a42 ("bpf: Add batch ops to all htab bpf map")
>

Fixes tag can be added by the maintainers when they pick it, but I
personally am not a fan of adding a Fixes tag for such a minor fix
here.

It is purely a syntactic change and change for the sparse semantic
parser, but it really does not need to be backported and nothing
observable in the binary was broken.

That is my rationale for not adding a Fixes: tag here. It is your final call.

> >
> > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
>
> Thanks for the fix. LGTM. I guess either bpf or bpf-next tree is fine
> since this is not a correctness issue.
>

Agree, and it is no functional change, nor a change in the object
code. So risks of regressions are very, very low (zero).

Thanks for the review,

Lukas

Re: [PATCH] bpf: propagate __user annotations properly

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (refs/heads/master):

On Mon,  7 Dec 2020 13:37:20 +0100 you wrote:
> __htab_map_lookup_and_delete_batch() stores a user pointer in the local
> variable ubatch and uses that in copy_{from,to}_user(), but ubatch misses a
> __user annotation.
> 
> So, sparse warns in the various assignments and uses of ubatch:
> 
>   kernel/bpf/hashtab.c:1415:24: warning: incorrect type in initializer
>     (different address spaces)
>   kernel/bpf/hashtab.c:1415:24:    expected void *ubatch
>   kernel/bpf/hashtab.c:1415:24:    got void [noderef] __user *
> 
> [...]

Here is the summary with links:
  - bpf: propagate __user annotations properly
    https://git.kernel.org/bpf/bpf-next/c/2f4b03195fe8

You are awesome, thank you!
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