[PATCH bpf] libbpf: fix potential NULL pointer dereference

[Ciara Loftus]

Wait until after the UMEM is checked for null to dereference it.

Fixes: 43f1bc1efff1 ("libbpf: Restore umem state after socket create failure")

Signed-off-by: Ciara Loftus <ciara.lof...@intel.com>
---
 tools/lib/bpf/xsk.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index d24b5cc720ec..770040d1f893 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -858,12 +858,14 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
        struct xsk_socket *xsk;
        struct xsk_ctx *ctx;
        int err, ifindex;
-       bool unmap = umem->fill_save != fill;
+       bool unmap;
        bool rx_setup_done = false, tx_setup_done = false;
 
        if (!umem || !xsk_ptr || !(rx || tx))
                return -EFAULT;
 
+       unmap = umem->fill_save != fill;
+
        xsk = calloc(1, sizeof(*xsk));
        if (!xsk)
                return -ENOMEM;
-- 
2.17.1