* [PATCH bpf] xsk: add missing check on user supplied headroom size
@ 2020-04-14 7:35 Magnus Karlsson
2020-04-15 12:33 ` Daniel Borkmann
0 siblings, 1 reply; 2+ messages in thread
From: Magnus Karlsson @ 2020-04-14 7:35 UTC (permalink / raw)
To: magnus.karlsson, bjorn.topel, ast, daniel, netdev, jonathan.lemon
Cc: minhquangbui99, bpf
Add a check that the headroom cannot be larger than the available
space in the chunk. In the current code, a malicious user can set the
headroom to a value larger than the chunk size minus the fixed XDP
headroom. That way packets with a length larger than the supported
size in the umem could get accepted and result in an out-of-bounds
write.
Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Reported-by: Bui Quang Minh <minhquangbui99@gmail.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=207225
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
net/xdp/xdp_umem.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index fa7bb5e..ed7a606 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -343,7 +343,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
unsigned int chunks, chunks_per_page;
u64 addr = mr->addr, size = mr->len;
- int size_chk, err;
+ int err;
if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
/* Strictly speaking we could support this, if:
@@ -382,8 +382,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
return -EINVAL;
}
- size_chk = chunk_size - headroom - XDP_PACKET_HEADROOM;
- if (size_chk < 0)
+ if (headroom >= chunk_size - XDP_PACKET_HEADROOM)
return -EINVAL;
umem->address = (unsigned long)addr;
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH bpf] xsk: add missing check on user supplied headroom size
2020-04-14 7:35 [PATCH bpf] xsk: add missing check on user supplied headroom size Magnus Karlsson
@ 2020-04-15 12:33 ` Daniel Borkmann
0 siblings, 0 replies; 2+ messages in thread
From: Daniel Borkmann @ 2020-04-15 12:33 UTC (permalink / raw)
To: Magnus Karlsson, bjorn.topel, ast, netdev, jonathan.lemon
Cc: minhquangbui99, bpf
On 4/14/20 9:35 AM, Magnus Karlsson wrote:
> Add a check that the headroom cannot be larger than the available
> space in the chunk. In the current code, a malicious user can set the
> headroom to a value larger than the chunk size minus the fixed XDP
> headroom. That way packets with a length larger than the supported
> size in the umem could get accepted and result in an out-of-bounds
> write.
>
> Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
> Reported-by: Bui Quang Minh <minhquangbui99@gmail.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=207225
> Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Applied, thanks everyone!
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