* [PATCH bpf] xsk: add overflow check for u64 division, stored into u32
@ 2020-05-25 8:03 Björn Töpel
2020-05-25 18:30 ` Jonathan Lemon
2020-05-25 22:19 ` Daniel Borkmann
0 siblings, 2 replies; 3+ messages in thread
From: Björn Töpel @ 2020-05-25 8:03 UTC (permalink / raw)
To: magnus.karlsson, jonathan.lemon, ast, daniel, netdev, bpf
Cc: Björn Töpel, maximmi, Minh Bùi Quang
From: Björn Töpel <bjorn.topel@intel.com>
The npgs member of struct xdp_umem is an u32 entity, and stores the
number of pages the UMEM consumes. The calculation of npgs
npgs = size / PAGE_SIZE
can overflow.
To avoid overflow scenarios, the division is now first stored in a
u64, and the result is verified to fit into 32b.
An alternative would be storing the npgs as a u64, however, this
wastes memory and is an unrealisticly large packet area.
Link: https://lore.kernel.org/bpf/CACtPs=GGvV-_Yj6rbpzTVnopgi5nhMoCcTkSkYrJHGQHJWFZMQ@mail.gmail.com/
Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Reported-by: "Minh Bùi Quang" <minhquangbui99@gmail.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
net/xdp/xdp_umem.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index ed7a6060f73c..3889bd9aec46 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -341,8 +341,8 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
{
bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
+ u64 npgs, addr = mr->addr, size = mr->len;
unsigned int chunks, chunks_per_page;
- u64 addr = mr->addr, size = mr->len;
int err;
if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
@@ -372,6 +372,10 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
if ((addr + size) < addr)
return -EINVAL;
+ npgs = div_u64(size, PAGE_SIZE);
+ if (npgs > U32_MAX)
+ return -EINVAL;
+
chunks = (unsigned int)div_u64(size, chunk_size);
if (chunks == 0)
return -EINVAL;
@@ -391,7 +395,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
umem->size = size;
umem->headroom = headroom;
umem->chunk_size_nohr = chunk_size - headroom;
- umem->npgs = size / PAGE_SIZE;
+ umem->npgs = (u32)npgs;
umem->pgs = NULL;
umem->user = NULL;
umem->flags = mr->flags;
base-commit: d04322a0da1e86aedaa322ce933cfb8c0191d1eb
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH bpf] xsk: add overflow check for u64 division, stored into u32
2020-05-25 8:03 [PATCH bpf] xsk: add overflow check for u64 division, stored into u32 Björn Töpel
@ 2020-05-25 18:30 ` Jonathan Lemon
2020-05-25 22:19 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Jonathan Lemon @ 2020-05-25 18:30 UTC (permalink / raw)
To: Björn Töpel
Cc: magnus.karlsson, jonathan.lemon, ast, daniel, netdev, bpf,
Björn Töpel, maximmi, Minh Bùi Quang
On Mon, May 25, 2020 at 10:03:59AM +0200, Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
>
> The npgs member of struct xdp_umem is an u32 entity, and stores the
> number of pages the UMEM consumes. The calculation of npgs
>
> npgs = size / PAGE_SIZE
>
> can overflow.
>
> To avoid overflow scenarios, the division is now first stored in a
> u64, and the result is verified to fit into 32b.
>
> An alternative would be storing the npgs as a u64, however, this
> wastes memory and is an unrealisticly large packet area.
>
> Link: https://lore.kernel.org/bpf/CACtPs=GGvV-_Yj6rbpzTVnopgi5nhMoCcTkSkYrJHGQHJWFZMQ@mail.gmail.com/
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: "Minh Bùi Quang" <minhquangbui99@gmail.com>
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH bpf] xsk: add overflow check for u64 division, stored into u32
2020-05-25 8:03 [PATCH bpf] xsk: add overflow check for u64 division, stored into u32 Björn Töpel
2020-05-25 18:30 ` Jonathan Lemon
@ 2020-05-25 22:19 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2020-05-25 22:19 UTC (permalink / raw)
To: Björn Töpel, magnus.karlsson, jonathan.lemon, ast, netdev, bpf
Cc: Björn Töpel, maximmi, Minh Bùi Quang
On 5/25/20 10:03 AM, Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@intel.com>
>
> The npgs member of struct xdp_umem is an u32 entity, and stores the
> number of pages the UMEM consumes. The calculation of npgs
>
> npgs = size / PAGE_SIZE
>
> can overflow.
>
> To avoid overflow scenarios, the division is now first stored in a
> u64, and the result is verified to fit into 32b.
>
> An alternative would be storing the npgs as a u64, however, this
> wastes memory and is an unrealisticly large packet area.
>
> Link: https://lore.kernel.org/bpf/CACtPs=GGvV-_Yj6rbpzTVnopgi5nhMoCcTkSkYrJHGQHJWFZMQ@mail.gmail.com/
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: "Minh Bùi Quang" <minhquangbui99@gmail.com>
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Applied, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-05-25 22:19 ` Daniel Borkmann
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