From: Maciej Fijalkowski maciej.fijalkowski@intel.com
[ Upstream commit 39e940d4abfabb08b6937a315546b24d10be67e3 ]
Currently, xsk_socket__delete frees BPF resources regardless of ctx refcount. Xdpxceiver has a test to verify whether underlying BPF resources would not be wiped out after closing XSK socket that was bound to interface with other active sockets. From library's xsk part perspective it also means that the internal xsk context is shared and its refcount is bumped accordingly.
After a switch to loading XDP prog based on previously opened XSK socket, mentioned xdpxceiver test fails with:
not ok 16 [xdpxceiver.c:swap_xsk_resources:1334]: ERROR: 9/"Bad file descriptor
which means that in swap_xsk_resources(), xsk_socket__delete() released xskmap which in turn caused a failure of xsk_socket__update_xskmap().
To fix this, when deleting socket, decrement ctx refcount before releasing BPF resources and do so only when refcount dropped to 0 which means there are no more active sockets for this ctx so BPF resources can be freed safely.
Fixes: 2f6324a3937f ("libbpf: Support shared umems between queues and devices") Signed-off-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Magnus Karlsson magnus.karlsson@intel.com Link: https://lore.kernel.org/bpf/20220629143458.934337-5-maciej.fijalkowski@intel... Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/xsk.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c index a27b3141463a..42b8437b0535 100644 --- a/tools/lib/bpf/xsk.c +++ b/tools/lib/bpf/xsk.c @@ -1164,8 +1164,6 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr, goto out_mmap_tx; }
- ctx->prog_fd = -1; - if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) { err = __xsk_setup_xdp_prog(xsk, NULL); if (err) @@ -1246,7 +1244,10 @@ void xsk_socket__delete(struct xsk_socket *xsk)
ctx = xsk->ctx; umem = ctx->umem; - if (ctx->prog_fd != -1) { + + xsk_put_ctx(ctx, true); + + if (!ctx->refcount) { xsk_delete_bpf_maps(xsk); close(ctx->prog_fd); if (ctx->has_bpf_link) @@ -1265,8 +1266,6 @@ void xsk_socket__delete(struct xsk_socket *xsk) } }
- xsk_put_ctx(ctx, true); - umem->refcount--; /* Do not close an fd that also has an associated umem connected * to it.