Currently when packet is shrunk via bpf_xdp_adjust_tail(), null ptr
dereference happens:
[1136314.192256] BUG: kernel NULL pointer dereference, address:
0000000000000034
[1136314.203943] #PF: supervisor read access in kernel mode
[1136314.213768] #PF: error_code(0x0000) - not-present page
[1136314.223550] PGD 0 P4D 0
[1136314.230684] Oops: 0000 [#1] PREEMPT SMP NOPTI
[1136314.239621] CPU: 8 PID: 54203 Comm: xdpsock Not tainted 6.6.0+ #257
[1136314.250469] Hardware name: Intel Corporation S2600WFT/S2600WFT,
BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019
[1136314.265615] RIP: 0010:__xdp_return+0x6c/0x210
[1136314.274653] Code: ad 00 48 8b 47 08 49 89 f8 a8 01 0f 85 9b 01 00 00 0f 1f 44 00 00 f0 41 ff 48 34 75 32 4c 89 c7 e9 79 cd 80 ff 83 fe 03 75 17 <f6> 41 34 01 0f 85 02 01 00 00 48 89 cf e9 22 cc 1e 00 e9 3d d2 86
[1136314.302907] RSP: 0018:ffffc900089f8db0 EFLAGS: 00010246
[1136314.312967] RAX: ffffc9003168aed0 RBX: ffff8881c3300000 RCX:
0000000000000000
[1136314.324953] RDX: 0000000000000000 RSI: 0000000000000003 RDI:
ffffc9003168c000
[1136314.336929] RBP: 0000000000000ae0 R08: 0000000000000002 R09:
0000000000010000
[1136314.348844] R10: ffffc9000e495000 R11: 0000000000000040 R12:
0000000000000001
[1136314.360706] R13: 0000000000000524 R14: ffffc9003168aec0 R15:
0000000000000001
[1136314.373298] FS: 00007f8df8bbcb80(0000) GS:ffff8897e0e00000(0000)
knlGS:0000000000000000
[1136314.386105] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[1136314.396532] CR2: 0000000000000034 CR3: 00000001aa912002 CR4:
00000000007706f0
[1136314.408377] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[1136314.420173] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[1136314.431890] PKRU: 55555554
[1136314.439143] Call Trace:
[1136314.446058] <IRQ>
[1136314.452465] ? __die+0x20/0x70
[1136314.459881] ? page_fault_oops+0x15b/0x440
[1136314.468305] ? exc_page_fault+0x6a/0x150
[1136314.476491] ? asm_exc_page_fault+0x22/0x30
[1136314.484927] ? __xdp_return+0x6c/0x210
[1136314.492863] bpf_xdp_adjust_tail+0x155/0x1d0
[1136314.501269] bpf_prog_ccc47ae29d3b6570_xdp_sock_prog+0x15/0x60
[1136314.511263] ice_clean_rx_irq_zc+0x206/0xc60 [ice]
[1136314.520222] ? ice_xmit_zc+0x6e/0x150 [ice]
[1136314.528506] ice_napi_poll+0x467/0x670 [ice]
[1136314.536858] ? ttwu_do_activate.constprop.0+0x8f/0x1a0
[1136314.546010] __napi_poll+0x29/0x1b0
[1136314.553462] net_rx_action+0x133/0x270
[1136314.561619] __do_softirq+0xbe/0x28e
[1136314.569303] do_softirq+0x3f/0x60
This comes from __xdp_return() call with xdp_buff argument passed as
NULL which is supposed to be consumed by xsk_buff_free() call.
To address this properly, in ZC case, a node that represents the frag
being removed has to be pulled out of xskb_list. Introduce
appriopriate xsk helpers to do such node operation and use them
accordingly within bpf_xdp_adjust_tail().
Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
---
include/net/xdp_sock_drv.h | 26 +++++++++++++++++++++
net/core/filter.c | 48 +++++++++++++++++++++++++++++++-------
2 files changed, 65 insertions(+), 9 deletions(-)
diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 81e02de3f453..123adc6d68c1 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -147,6 +147,23 @@ static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
return ret;
}
+static inline void xsk_buff_tail_del(struct xdp_buff *tail)
+{
+ struct xdp_buff_xsk *xskb = container_of(tail, struct xdp_buff_xsk, xdp);
+
+ list_del(&xskb->xskb_list_node);
+}
+
+static inline struct xdp_buff *xsk_buff_get_tail(struct xdp_buff *first)
+{
+ struct xdp_buff_xsk *xskb = container_of(first, struct xdp_buff_xsk, xdp);
+ struct xdp_buff_xsk *frag;
+
+ frag = list_last_entry(&xskb->pool->xskb_list, struct xdp_buff_xsk,
+ xskb_list_node);
+ return &frag->xdp;
+}
+
static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
{
xdp->data = xdp->data_hard_start + XDP_PACKET_HEADROOM;
@@ -333,6 +350,15 @@ static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
return NULL;
}
+static inline void xsk_buff_tail_del(struct xdp_buff *tail)
+{
+}
+
+static inline struct xdp_buff *xsk_buff_get_tail(struct xdp_buff *first)
+{
+ return NULL;
+}
+
static inline void xsk_buff_set_size(struct xdp_buff *xdp, u32 size)
{
}
diff --git a/net/core/filter.c b/net/core/filter.c
index adcfc2c25754..8ce13d73a660 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -83,6 +83,7 @@
#include <net/netfilter/nf_conntrack_bpf.h>
#include <net/netkit.h>
#include <linux/un.h>
+#include <net/xdp_sock_drv.h>
#include "dev.h"
@@ -4075,6 +4076,42 @@ static int bpf_xdp_frags_increase_tail(struct xdp_buff *xdp, int offset)
return 0;
}
+static void __shrink_data(struct xdp_buff *xdp, struct xdp_mem_info *mem_info,
+ skb_frag_t *frag, int shrink)
+{
+ if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL) {
+ struct xdp_buff *tail = xsk_buff_get_tail(xdp);
+
+ if (tail)
+ tail->data_end -= shrink;
+ }
+ skb_frag_size_sub(frag, shrink);
+}
+
+static bool shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, int shrink)
+{
+ struct xdp_mem_info *mem_info = &xdp->rxq->mem;
+
+ if (skb_frag_size(frag) == shrink) {
+ struct page *page = skb_frag_page(frag);
+ struct xdp_buff *zc_frag = NULL;
+
+ if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL) {
+ zc_frag = xsk_buff_get_tail(xdp);
+
+ if (zc_frag) {
+ xdp_buff_clear_frags_flag(zc_frag);
+ xsk_buff_tail_del(zc_frag);
+ }
+ }
+
+ __xdp_return(page_address(page), mem_info, false, zc_frag);
+ return true;
+ }
+ __shrink_data(xdp, mem_info, frag, shrink);
+ return false;
+}
+
static int bpf_xdp_frags_shrink_tail(struct xdp_buff *xdp, int offset)
{
struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
@@ -4089,17 +4126,10 @@ static int bpf_xdp_frags_shrink_tail(struct xdp_buff *xdp, int offset)
len_free += shrink;
offset -= shrink;
-
- if (skb_frag_size(frag) == shrink) {
- struct page *page = skb_frag_page(frag);
-
- __xdp_return(page_address(page), &xdp->rxq->mem,
- false, NULL);
+ if (shrink_data(xdp, frag, shrink))
n_frags_free++;
- } else {
- skb_frag_size_sub(frag, shrink);
+ else
break;
- }
}
sinfo->nr_frags -= n_frags_free;
sinfo->xdp_frags_size -= len_free;
--
2.34.1
