From: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Fix a possible use after free in xsk_socket__delete that will happen
if xsk_put_ctx() frees the ctx. To fix, save the umem reference taken
from the context and just use that instead.
Fixes: 2f6324a3937f ("libbpf: Support shared umems between queues and devices")
Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
---
tools/lib/bpf/xsk.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 504b7a8..9bc537d 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -892,6 +892,7 @@ void xsk_socket__delete(struct xsk_socket *xsk)
{
size_t desc_sz = sizeof(struct xdp_desc);
struct xdp_mmap_offsets off;
+ struct xsk_umem *umem;
struct xsk_ctx *ctx;
int err;
@@ -899,6 +900,7 @@ void xsk_socket__delete(struct xsk_socket *xsk)
return;
ctx = xsk->ctx;
+ umem = ctx->umem;
if (ctx->prog_fd != -1) {
xsk_delete_bpf_maps(xsk);
close(ctx->prog_fd);
@@ -918,11 +920,11 @@ void xsk_socket__delete(struct xsk_socket *xsk)
xsk_put_ctx(ctx);
- ctx->umem->refcount--;
+ umem->refcount--;
/* Do not close an fd that also has an associated umem connected
* to it.
*/
- if (xsk->fd != ctx->umem->fd)
+ if (xsk->fd != umem->fd)
close(xsk->fd);
free(xsk);
}
--
2.7.4
