diff mbox series

[v5,bpf,03/11] xsk: fix usage of multi-buffer BPF helpers for ZC XDP

Message ID 20240122221610.556746-4-maciej.fijalkowski@intel.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series net: bpf_xdp_adjust_tail() and Intel mbuf fixes | expand

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Commit Message

Maciej Fijalkowski Jan. 22, 2024, 10:16 p.m. UTC 
Currently when packet is shrunk via bpf_xdp_adjust_tail() and memory
type is set to MEM_TYPE_XSK_BUFF_POOL, 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")
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com> # For the xsk header part
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 include/net/xdp_sock_drv.h | 26 ++++++++++++++++++++++++
 net/core/filter.c          | 41 +++++++++++++++++++++++++++++---------
 2 files changed, 58 insertions(+), 9 deletions(-)

Comments

Jakub Kicinski Jan. 24, 2024, 1:53 a.m. UTC | #1 
On Mon, 22 Jan 2024 23:16:02 +0100 Maciej Fijalkowski wrote:
>  
> +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)
> +		xsk_buff_get_tail(xdp)->data_end -= shrink;
> +	skb_frag_size_sub(frag, shrink);

nit: this has just one caller, why not inline these 3 lines?

> +}
> +
> +static bool shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, int shrink)

nit: prefix the function name, please

> +{
> +	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);
> +
> +			xsk_buff_del_tail(zc_frag);
> +		}
> +
> +		__xdp_return(page_address(page), mem_info, false, zc_frag);
> +		return true;
> +	}
> +	__shrink_data(xdp, mem_info, frag, shrink);
> +	return false;
Maciej Fijalkowski Jan. 24, 2024, 12:02 p.m. UTC | #2 
On Tue, Jan 23, 2024 at 05:53:17PM -0800, Jakub Kicinski wrote:
> On Mon, 22 Jan 2024 23:16:02 +0100 Maciej Fijalkowski wrote:
> >  
> > +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)
> > +		xsk_buff_get_tail(xdp)->data_end -= shrink;
> > +	skb_frag_size_sub(frag, shrink);
> 
> nit: this has just one caller, why not inline these 3 lines?

we usually rely on compiler to do that, we have the rule "no inlines in
source files", no?

> 
> > +}
> > +
> > +static bool shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, int shrink)
> 
> nit: prefix the function name, please

will rename to bpf_xdp_shrink_data(). Thanks for taking a look!

> 
> > +{
> > +	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);
> > +
> > +			xsk_buff_del_tail(zc_frag);
> > +		}
> > +
> > +		__xdp_return(page_address(page), mem_info, false, zc_frag);
> > +		return true;
> > +	}
> > +	__shrink_data(xdp, mem_info, frag, shrink);
> > +	return false;
Jakub Kicinski Jan. 24, 2024, 4:53 p.m. UTC | #3 
On Wed, 24 Jan 2024 13:02:21 +0100 Maciej Fijalkowski wrote:
> > nit: this has just one caller, why not inline these 3 lines?  
> 
> we usually rely on compiler to do that, we have the rule "no inlines in
> source files", no?

I mean Ctrl-x Ctrl-v the code, the function has 3 LoC and one caller.
And a semi-meaningless name. I'm not sure why this code was factored
out.

> > nit: prefix the function name, please  
> 
> will rename to bpf_xdp_shrink_data(). Thanks for taking a look!
Maciej Fijalkowski Jan. 24, 2024, 4:56 p.m. UTC | #4 
On Wed, Jan 24, 2024 at 08:53:49AM -0800, Jakub Kicinski wrote:
> On Wed, 24 Jan 2024 13:02:21 +0100 Maciej Fijalkowski wrote:
> > > nit: this has just one caller, why not inline these 3 lines?  
> > 
> > we usually rely on compiler to do that, we have the rule "no inlines in
> > source files", no?
> 
> I mean Ctrl-x Ctrl-v the code, the function has 3 LoC and one caller.
> And a semi-meaningless name. I'm not sure why this code was factored
> out.

Ummm. Probably some previous version was heavier, now I see the point :)
Will fix.

> 
> > > nit: prefix the function name, please  
> > 
> > will rename to bpf_xdp_shrink_data(). Thanks for taking a look!
> 
>
diff mbox series

Patch

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index b62bb8525a5f..3d35ac0f838b 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -159,6 +159,23 @@  static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
 	return ret;
 }
 
+static inline void xsk_buff_del_tail(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;
@@ -350,6 +367,15 @@  static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
 	return NULL;
 }
 
+static inline void xsk_buff_del_tail(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 24061f29c9dd..8e0cd8ca461e 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"
 
@@ -4096,6 +4097,35 @@  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)
+		xsk_buff_get_tail(xdp)->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);
+
+			xsk_buff_del_tail(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);
@@ -4110,17 +4140,10 @@  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;