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xsk: Add missing check on user supplied headroom size 

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: c0c77d8fb7 ("xsk: add user memory registration support sockopt")
Reported-by: Bui Quang Minh <minhquangbui99@gmail.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=207225
Link: https://lore.kernel.org/bpf/1586849715-23490-1-git-send-email-magnus.karlsson@intel.com
This commit is contained in:
Magnus Karlsson 2020-04-14 09:35:15 +02:00 committed by Daniel Borkmann
parent 89f33dcadb
commit 99e3a236dd
1 changed files with 2 additions and 3 deletions
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5
net/xdp/xdp_umem.c
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@ -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;