The number of chunks can overflow u32. Make sure to return -EINVAL on
overflow.

Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
Signed-off-by: Kal Conley <kal.conley@dectris.com>
---
 net/xdp/xdp_umem.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 4681e8e8ad94..02207e852d79 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -150,10 +150,11 @@ static int xdp_umem_account_pages(struct xdp_umem *umem)
 
 static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 {
-	u32 npgs_rem, chunk_size = mr->chunk_size, headroom = mr->headroom;
 	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
-	u64 npgs, addr = mr->addr, size = mr->len;
-	unsigned int chunks, chunks_rem;
+	u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
+	u64 addr = mr->addr, size = mr->len;
+	u32 chunks_rem, npgs_rem;
+	u64 chunks, npgs;
 	int err;
 
 	if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
@@ -188,8 +189,8 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	if (npgs > U32_MAX)
 		return -EINVAL;
 
-	chunks = (unsigned int)div_u64_rem(size, chunk_size, &chunks_rem);
-	if (chunks == 0)
+	chunks = div_u64_rem(size, chunk_size, &chunks_rem);
+	if (!chunks || chunks > U32_MAX)
 		return -EINVAL;
 
 	if (!unaligned_chunks && chunks_rem)
@@ -202,7 +203,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	umem->headroom = headroom;
 	umem->chunk_size = chunk_size;
 	umem->chunks = chunks;
-	umem->npgs = (u32)npgs;
+	umem->npgs = npgs;
 	umem->pgs = NULL;
 	umem->user = NULL;
 	umem->flags = mr->flags;
-- 
2.39.2

From: Kal Conley <kal.conley@dectris.com>
Date: Wed,  8 Mar 2023 11:51:30 +0100

> [PATCH] xsk: Add missing overflow check in xdp_umem_reg

You need to mark it properly. It must've been

[PATCH bpf v2] xsk: Add missing overflow check in xdp_umem_reg

instead.

> The number of chunks can overflow u32. Make sure to return -EINVAL on
> overflow.

I'd mention here that cast removal, so that reviewers wouldn't ask why
you did this.

> 
> Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
> Signed-off-by: Kal Conley <kal.conley@dectris.com>
> ---
>  net/xdp/xdp_umem.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index 4681e8e8ad94..02207e852d79 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -150,10 +150,11 @@ static int xdp_umem_account_pages(struct xdp_umem *umem)
>  
>  static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
>  {
> -	u32 npgs_rem, chunk_size = mr->chunk_size, headroom = mr->headroom;
>  	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
> -	u64 npgs, addr = mr->addr, size = mr->len;
> -	unsigned int chunks, chunks_rem;
> +	u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
> +	u64 addr = mr->addr, size = mr->len;
> +	u32 chunks_rem, npgs_rem;
> +	u64 chunks, npgs;
>  	int err;
>  
>  	if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
> @@ -188,8 +189,8 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
>  	if (npgs > U32_MAX)
>  		return -EINVAL;
>  
> -	chunks = (unsigned int)div_u64_rem(size, chunk_size, &chunks_rem);
> -	if (chunks == 0)
> +	chunks = div_u64_rem(size, chunk_size, &chunks_rem);
> +	if (!chunks || chunks > U32_MAX)
>  		return -EINVAL;
>  
>  	if (!unaligned_chunks && chunks_rem)
> @@ -202,7 +203,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
>  	umem->headroom = headroom;
>  	umem->chunk_size = chunk_size;
>  	umem->chunks = chunks;
> -	umem->npgs = (u32)npgs;
> +	umem->npgs = npgs;
>  	umem->pgs = NULL;
>  	umem->user = NULL;
>  	umem->flags = mr->flags;

The code is fine to me.
Please resubmit with the fixed subject and expanded commit message.
I'd also prefer that you sent v3 as a separate mail, *not* as a reply to
this thread.

Thanks,
Olek

> The code is fine to me.
> Please resubmit with the fixed subject and expanded commit message.
> I'd also prefer that you sent v3 as a separate mail, *not* as a reply to
> this thread.

Done. I used "bpf" in the subject as you suggested, however I am a bit
confused by this. Should changes under net/xdp generally use "bpf" in
the subject?

Thanks,
Kal

From: Kal Conley <kal.conley@dectris.com>
Date: Wed, 8 Mar 2023 19:49:29 +0100

>> The code is fine to me.
>> Please resubmit with the fixed subject and expanded commit message.
>> I'd also prefer that you sent v3 as a separate mail, *not* as a reply to
>> this thread.
> 
> Done. I used "bpf" in the subject as you suggested, however I am a bit
> confused by this. Should changes under net/xdp generally use "bpf" in
> the subject?

"bpf" when it's a fix (better to have some real repro, otherwise purely
hypothetical fix can be considered a bpf-next material), "bpf-next" when
it's an improvement / new stuff etc.

Also please don't forget to manually add all the folks who reviewed your
previous versions / were participating in the threads for previous
versions, otherwise they can miss the fact that you posted a new revision.

> 
> Thanks,
> Kal

Thanks,
Olek