[PATCH 5.11 077/122] libbpf: Fix potential NULL pointer dereference

Greg Kroah-Hartman
2021-04-19T13:12:58Z

From: Ciara Loftus <ciara.loftus@intel.com>

commit afd0be7299533bb2e2b09104399d8a467ecbd2c5 upstream.

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.loftus@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210408052009.7844-1-ciara.loftus@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/lib/bpf/xsk.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -777,18 +777,19 @@ int xsk_socket__create_shared(struct xsk
struct xsk_ring_cons *comp,
const struct xsk_socket_config *usr_config)
{
+ bool unmap, rx_setup_done = false, tx_setup_done = false;
void *rx_map = NULL, *tx_map = NULL;
struct sockaddr_xdp sxdp = {};
struct xdp_mmap_offsets off;
struct xsk_socket *xsk;
struct xsk_ctx *ctx;
int err, ifindex;
- bool unmap = umem->fill_save != fill;
- 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;