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authorJesper Dangaard Brouer <brouer@redhat.com>2020-05-14 12:49:33 +0200
committerAlexei Starovoitov <ast@kernel.org>2020-05-15 06:21:54 +0200
commit34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a (patch)
treefb51ed98a7080db136df2260b9de579b645482ef /include/net/xdp.h
parentnet: XDP-generic determining XDP frame size (diff)
downloadlinux-34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a.tar.xz
linux-34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a.zip
xdp: Xdp_frame add member frame_sz and handle in convert_to_xdp_frame
Use hole in struct xdp_frame, when adding member frame_sz, which keeps same sizeof struct (32 bytes) Drivers ixgbe and sfc had bug cases where the necessary/expected tailroom was not reserved. This can lead to some hard to catch memory corruption issues. Having the drivers frame_sz this can be detected when packet length/end via xdp->data_end exceed the xdp_data_hard_end pointer, which accounts for the reserved the tailroom. When detecting this driver issue, simply fail the conversion with NULL, which results in feedback to driver (failing xdp_do_redirect()) causing driver to drop packet. Given the lack of consistent XDP stats, this can be hard to troubleshoot. And given this is a driver bug, we want to generate some more noise in form of a WARN stack dump (to ID the driver code that inlined convert_to_xdp_frame). Inlining the WARN macro is problematic, because it adds an asm instruction (on Intel CPUs ud2) what influence instruction cache prefetching. Thus, introduce xdp_warn and macro XDP_WARN, to avoid this and at the same time make identifying the function and line of this inlined function easier. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/bpf/158945337313.97035.10015729316710496600.stgit@firesoul
Diffstat (limited to 'include/net/xdp.h')
-rw-r--r--include/net/xdp.h14
1 files changed, 13 insertions, 1 deletions
diff --git a/include/net/xdp.h b/include/net/xdp.h
index a764af4ae0ea..3094fccf5a88 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -89,7 +89,8 @@ struct xdp_frame {
void *data;
u16 len;
u16 headroom;
- u16 metasize;
+ u32 metasize:8;
+ u32 frame_sz:24;
/* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time,
* while mem info is valid on remote CPU.
*/
@@ -104,6 +105,10 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame)
frame->dev_rx = NULL;
}
+/* Avoids inlining WARN macro in fast-path */
+void xdp_warn(const char *msg, const char *func, const int line);
+#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__)
+
struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
/* Convert xdp_buff to xdp_frame */
@@ -124,6 +129,12 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
if (unlikely((headroom - metasize) < sizeof(*xdp_frame)))
return NULL;
+ /* Catch if driver didn't reserve tailroom for skb_shared_info */
+ if (unlikely(xdp->data_end > xdp_data_hard_end(xdp))) {
+ XDP_WARN("Driver BUG: missing reserved tailroom");
+ return NULL;
+ }
+
/* Store info in top of packet */
xdp_frame = xdp->data_hard_start;
@@ -131,6 +142,7 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
xdp_frame->len = xdp->data_end - xdp->data;
xdp_frame->headroom = headroom - sizeof(*xdp_frame);
xdp_frame->metasize = metasize;
+ xdp_frame->frame_sz = xdp->frame_sz;
/* rxq only valid until napi_schedule ends, convert to xdp_mem_info */
xdp_frame->mem = xdp->rxq->mem;