* [PATCH net 2/2] net: enetc: fix NTMP DMA use-after-free issue
2026-04-13 7:52 [PATCH net 0/2] net: enetc: fix command BD ring issues Wei Fang
2026-04-13 7:52 ` [PATCH net 1/2] net: enetc: correct the command BD ring consumer index Wei Fang
@ 2026-04-13 7:52 ` Wei Fang
1 sibling, 0 replies; 3+ messages in thread
From: Wei Fang @ 2026-04-13 7:52 UTC (permalink / raw)
To: claudiu.manoil, vladimir.oltean, xiaoning.wang, andrew+netdev,
davem, edumazet, kuba, pabeni, chleroy
Cc: netdev, linux-kernel, imx, linuxppc-dev, linux-arm-kernel
The AI-generated review reported a potential DMA use-after-free issue
[1]. If netc_xmit_ntmp_cmd() times out and returns an error, the pending
command is not explicitly aborted, while ntmp_free_data_mem()
unconditionally frees the DMA buffer. If the buffer has already been
reallocated elsewhere, this may lead to silent memory corruption. Because
the hardware eventually processes the pending command and perform a DMA
write of the response to the physical address of the freed buffer.
To resolve this issue, this patch does the following modifications:
1. Convert cbdr->ring_lock from a spinlock to a mutex
The lock was originally a spinlock in case NTMP operations might be
invoked from atomic context. After downstream support for all NTMP
tables, no such usage has materialized. A mutex lock is now required
because the driver now needs to reclaim used BDs and release associated
DMA memory within the lock's context, while dma_free_coherent() might
sleep.
2. Introduce software command BD (struct netc_swcbd)
The hardware write-back overwrites the addr and len fields of the BD,
so the driver cannot rely on the hardware BD to free the associated DMA
memory. The driver now maintains a software shadow BD storing the DMA
buffer pointer, DMA address, and size. And netc_xmit_ntmp_cmd() only
reclaims older BDs when the number of used BDs reaches
NETC_CBDR_CLEAN_WORK (16). The software BD enables correct DMA memory
release. With this, struct ntmp_dma_buf and ntmp_free_data_mem() are no
longer needed and are removed.
These changes eliminate the DMA use-after-free condition and ensure safe
and consistent BD reclamation and DMA buffer lifecycle management.
Fixes: 4701073c3deb ("net: enetc: add initial netc-lib driver to support NTMP")
Link: https://lore.kernel.org/netdev/20260403011729.1795413-1-kuba@kernel.org/ # [1]
Signed-off-by: Wei Fang <wei.fang@nxp.com>
---
drivers/net/ethernet/freescale/enetc/ntmp.c | 158 ++++++++++--------
.../ethernet/freescale/enetc/ntmp_private.h | 8 +-
include/linux/fsl/ntmp.h | 9 +-
3 files changed, 93 insertions(+), 82 deletions(-)
diff --git a/drivers/net/ethernet/freescale/enetc/ntmp.c b/drivers/net/ethernet/freescale/enetc/ntmp.c
index 1b1ff0446d0a..3efc65443113 100644
--- a/drivers/net/ethernet/freescale/enetc/ntmp.c
+++ b/drivers/net/ethernet/freescale/enetc/ntmp.c
@@ -7,6 +7,7 @@
#include <linux/dma-mapping.h>
#include <linux/fsl/netc_global.h>
#include <linux/iopoll.h>
+#include <linux/vmalloc.h>
#include "ntmp_private.h"
@@ -42,6 +43,12 @@ int ntmp_init_cbdr(struct netc_cbdr *cbdr, struct device *dev,
if (!cbdr->addr_base)
return -ENOMEM;
+ cbdr->swcbd = vcalloc(cbd_num, sizeof(struct netc_swcbd));
+ if (!cbdr->swcbd) {
+ dma_free_coherent(dev, size, cbdr->addr_base, cbdr->dma_base);
+ return -ENOMEM;
+ }
+
cbdr->dma_size = size;
cbdr->bd_num = cbd_num;
cbdr->regs = *regs;
@@ -52,7 +59,7 @@ int ntmp_init_cbdr(struct netc_cbdr *cbdr, struct device *dev,
cbdr->addr_base_align = PTR_ALIGN(cbdr->addr_base,
NTMP_BASE_ADDR_ALIGN);
- spin_lock_init(&cbdr->ring_lock);
+ mutex_init(&cbdr->ring_lock);
cbdr->next_to_use = netc_read(cbdr->regs.pir);
cbdr->next_to_clean = netc_read(cbdr->regs.cir) & NETC_CBDRCIR_INDEX;
@@ -71,10 +78,25 @@ int ntmp_init_cbdr(struct netc_cbdr *cbdr, struct device *dev,
}
EXPORT_SYMBOL_GPL(ntmp_init_cbdr);
+static void ntmp_free_data_mem(struct device *dev, struct netc_swcbd *swcbd)
+{
+ dma_free_coherent(dev, swcbd->size + NTMP_DATA_ADDR_ALIGN,
+ swcbd->buf, swcbd->dma);
+}
+
void ntmp_free_cbdr(struct netc_cbdr *cbdr)
{
/* Disable the Control BD Ring */
netc_write(cbdr->regs.mr, 0);
+
+ for (int i = 0; i < cbdr->bd_num; i++) {
+ struct netc_swcbd *swcbd = &cbdr->swcbd[i];
+
+ if (swcbd->dma)
+ ntmp_free_data_mem(cbdr->dev, swcbd);
+ }
+
+ vfree(cbdr->swcbd);
dma_free_coherent(cbdr->dev, cbdr->dma_size, cbdr->addr_base,
cbdr->dma_base);
memset(cbdr, 0, sizeof(*cbdr));
@@ -94,24 +116,28 @@ static union netc_cbd *ntmp_get_cbd(struct netc_cbdr *cbdr, int index)
static void ntmp_clean_cbdr(struct netc_cbdr *cbdr)
{
- union netc_cbd *cbd;
- int i;
+ int i = cbdr->next_to_clean;
- i = cbdr->next_to_clean;
while ((netc_read(cbdr->regs.cir) & NETC_CBDRCIR_INDEX) != i) {
- cbd = ntmp_get_cbd(cbdr, i);
+ union netc_cbd *cbd = ntmp_get_cbd(cbdr, i);
+ struct netc_swcbd *swcbd = &cbdr->swcbd[i];
+
+ ntmp_free_data_mem(cbdr->dev, swcbd);
+ memset(swcbd, 0, sizeof(*swcbd));
memset(cbd, 0, sizeof(*cbd));
i = (i + 1) % cbdr->bd_num;
}
+ dma_wmb();
cbdr->next_to_clean = i;
}
-static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd)
+static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd,
+ struct netc_swcbd *swcbd)
{
union netc_cbd *cur_cbd;
struct netc_cbdr *cbdr;
- int i, err;
+ int i, err, used_bds;
u16 status;
u32 val;
@@ -120,14 +146,21 @@ static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd)
*/
cbdr = &user->ring[0];
- spin_lock_bh(&cbdr->ring_lock);
+ mutex_lock(&cbdr->ring_lock);
- if (unlikely(!ntmp_get_free_cbd_num(cbdr)))
+ used_bds = cbdr->bd_num - ntmp_get_free_cbd_num(cbdr);
+ if (unlikely(used_bds >= NETC_CBDR_CLEAN_WORK)) {
ntmp_clean_cbdr(cbdr);
+ if (unlikely(!ntmp_get_free_cbd_num(cbdr))) {
+ err = -EBUSY;
+ goto cbdr_unlock;
+ }
+ }
i = cbdr->next_to_use;
cur_cbd = ntmp_get_cbd(cbdr, i);
*cur_cbd = *cbd;
+ cbdr->swcbd[i] = *swcbd;
dma_wmb();
/* Update producer index of both software and hardware */
@@ -135,10 +168,9 @@ static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd)
cbdr->next_to_use = i;
netc_write(cbdr->regs.pir, i);
- err = read_poll_timeout_atomic(netc_read, val,
- (val & NETC_CBDRCIR_INDEX) == i,
- NETC_CBDR_DELAY_US, NETC_CBDR_TIMEOUT,
- true, cbdr->regs.cir);
+ err = read_poll_timeout(netc_read, val, (val & NETC_CBDRCIR_INDEX) == i,
+ NETC_CBDR_DELAY_US, NETC_CBDR_TIMEOUT,
+ true, cbdr->regs.cir);
if (unlikely(err))
goto cbdr_unlock;
@@ -155,36 +187,28 @@ static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd)
dev_err(user->dev, "Command BD error: 0x%04x\n", status);
}
- ntmp_clean_cbdr(cbdr);
- dma_wmb();
-
cbdr_unlock:
- spin_unlock_bh(&cbdr->ring_lock);
+ mutex_unlock(&cbdr->ring_lock);
return err;
}
-static int ntmp_alloc_data_mem(struct ntmp_dma_buf *data, void **buf_align)
+static int ntmp_alloc_data_mem(struct device *dev, struct netc_swcbd *swcbd,
+ void **buf_align)
{
void *buf;
- buf = dma_alloc_coherent(data->dev, data->size + NTMP_DATA_ADDR_ALIGN,
- &data->dma, GFP_KERNEL);
+ buf = dma_alloc_coherent(dev, swcbd->size + NTMP_DATA_ADDR_ALIGN,
+ &swcbd->dma, GFP_KERNEL);
if (!buf)
return -ENOMEM;
- data->buf = buf;
+ swcbd->buf = buf;
*buf_align = PTR_ALIGN(buf, NTMP_DATA_ADDR_ALIGN);
return 0;
}
-static void ntmp_free_data_mem(struct ntmp_dma_buf *data)
-{
- dma_free_coherent(data->dev, data->size + NTMP_DATA_ADDR_ALIGN,
- data->buf, data->dma);
-}
-
static void ntmp_fill_request_hdr(union netc_cbd *cbd, dma_addr_t dma,
int len, int table_id, int cmd,
int access_method)
@@ -235,37 +259,36 @@ static int ntmp_delete_entry_by_id(struct ntmp_user *user, int tbl_id,
u8 tbl_ver, u32 entry_id, u32 req_len,
u32 resp_len)
{
- struct ntmp_dma_buf data = {
- .dev = user->dev,
+ struct netc_swcbd swcbd = {
.size = max(req_len, resp_len),
};
struct ntmp_req_by_eid *req;
union netc_cbd cbd;
int err;
- err = ntmp_alloc_data_mem(&data, (void **)&req);
+ err = ntmp_alloc_data_mem(user->dev, &swcbd, (void **)&req);
if (err)
return err;
ntmp_fill_crd_eid(req, tbl_ver, 0, 0, entry_id);
- ntmp_fill_request_hdr(&cbd, data.dma, NTMP_LEN(req_len, resp_len),
+ ntmp_fill_request_hdr(&cbd, swcbd.dma, NTMP_LEN(req_len, resp_len),
tbl_id, NTMP_CMD_DELETE, NTMP_AM_ENTRY_ID);
- err = netc_xmit_ntmp_cmd(user, &cbd);
+ err = netc_xmit_ntmp_cmd(user, &cbd, &swcbd);
if (err)
dev_err(user->dev,
"Failed to delete entry 0x%x of %s, err: %pe",
entry_id, ntmp_table_name(tbl_id), ERR_PTR(err));
- ntmp_free_data_mem(&data);
-
return err;
}
static int ntmp_query_entry_by_id(struct ntmp_user *user, int tbl_id,
- u32 len, struct ntmp_req_by_eid *req,
- dma_addr_t dma, bool compare_eid)
+ struct ntmp_req_by_eid *req,
+ struct netc_swcbd *swcbd,
+ bool compare_eid)
{
+ u32 len = NTMP_LEN(sizeof(*req), swcbd->size);
struct ntmp_cmn_resp_query *resp;
int cmd = NTMP_CMD_QUERY;
union netc_cbd cbd;
@@ -277,8 +300,9 @@ static int ntmp_query_entry_by_id(struct ntmp_user *user, int tbl_id,
cmd = NTMP_CMD_QU;
/* Request header */
- ntmp_fill_request_hdr(&cbd, dma, len, tbl_id, cmd, NTMP_AM_ENTRY_ID);
- err = netc_xmit_ntmp_cmd(user, &cbd);
+ ntmp_fill_request_hdr(&cbd, swcbd->dma, len, tbl_id, cmd,
+ NTMP_AM_ENTRY_ID);
+ err = netc_xmit_ntmp_cmd(user, &cbd, swcbd);
if (err) {
dev_err(user->dev,
"Failed to query entry 0x%x of %s, err: %pe\n",
@@ -306,15 +330,14 @@ static int ntmp_query_entry_by_id(struct ntmp_user *user, int tbl_id,
int ntmp_maft_add_entry(struct ntmp_user *user, u32 entry_id,
struct maft_entry_data *maft)
{
- struct ntmp_dma_buf data = {
- .dev = user->dev,
+ struct netc_swcbd swcbd = {
.size = sizeof(struct maft_req_add),
};
struct maft_req_add *req;
union netc_cbd cbd;
int err;
- err = ntmp_alloc_data_mem(&data, (void **)&req);
+ err = ntmp_alloc_data_mem(user->dev, &swcbd, (void **)&req);
if (err)
return err;
@@ -323,15 +346,13 @@ int ntmp_maft_add_entry(struct ntmp_user *user, u32 entry_id,
req->keye = maft->keye;
req->cfge = maft->cfge;
- ntmp_fill_request_hdr(&cbd, data.dma, NTMP_LEN(data.size, 0),
+ ntmp_fill_request_hdr(&cbd, swcbd.dma, NTMP_LEN(swcbd.size, 0),
NTMP_MAFT_ID, NTMP_CMD_ADD, NTMP_AM_ENTRY_ID);
- err = netc_xmit_ntmp_cmd(user, &cbd);
+ err = netc_xmit_ntmp_cmd(user, &cbd, &swcbd);
if (err)
dev_err(user->dev, "Failed to add MAFT entry 0x%x, err: %pe\n",
entry_id, ERR_PTR(err));
- ntmp_free_data_mem(&data);
-
return err;
}
EXPORT_SYMBOL_GPL(ntmp_maft_add_entry);
@@ -339,33 +360,27 @@ EXPORT_SYMBOL_GPL(ntmp_maft_add_entry);
int ntmp_maft_query_entry(struct ntmp_user *user, u32 entry_id,
struct maft_entry_data *maft)
{
- struct ntmp_dma_buf data = {
- .dev = user->dev,
+ struct netc_swcbd swcbd = {
.size = sizeof(struct maft_resp_query),
};
struct maft_resp_query *resp;
struct ntmp_req_by_eid *req;
int err;
- err = ntmp_alloc_data_mem(&data, (void **)&req);
+ err = ntmp_alloc_data_mem(user->dev, &swcbd, (void **)&req);
if (err)
return err;
ntmp_fill_crd_eid(req, user->tbl.maft_ver, 0, 0, entry_id);
- err = ntmp_query_entry_by_id(user, NTMP_MAFT_ID,
- NTMP_LEN(sizeof(*req), data.size),
- req, data.dma, true);
+ err = ntmp_query_entry_by_id(user, NTMP_MAFT_ID, req, &swcbd, true);
if (err)
- goto end;
+ return err;
resp = (struct maft_resp_query *)req;
maft->keye = resp->keye;
maft->cfge = resp->cfge;
-end:
- ntmp_free_data_mem(&data);
-
- return err;
+ return 0;
}
EXPORT_SYMBOL_GPL(ntmp_maft_query_entry);
@@ -379,8 +394,8 @@ EXPORT_SYMBOL_GPL(ntmp_maft_delete_entry);
int ntmp_rsst_update_entry(struct ntmp_user *user, const u32 *table,
int count)
{
- struct ntmp_dma_buf data = {.dev = user->dev};
struct rsst_req_update *req;
+ struct netc_swcbd swcbd;
union netc_cbd cbd;
int err, i;
@@ -388,8 +403,8 @@ int ntmp_rsst_update_entry(struct ntmp_user *user, const u32 *table,
/* HW only takes in a full 64 entry table */
return -EINVAL;
- data.size = struct_size(req, groups, count);
- err = ntmp_alloc_data_mem(&data, (void **)&req);
+ swcbd.size = struct_size(req, groups, count);
+ err = ntmp_alloc_data_mem(user->dev, &swcbd, (void **)&req);
if (err)
return err;
@@ -399,24 +414,22 @@ int ntmp_rsst_update_entry(struct ntmp_user *user, const u32 *table,
for (i = 0; i < count; i++)
req->groups[i] = (u8)(table[i]);
- ntmp_fill_request_hdr(&cbd, data.dma, NTMP_LEN(data.size, 0),
+ ntmp_fill_request_hdr(&cbd, swcbd.dma, NTMP_LEN(swcbd.size, 0),
NTMP_RSST_ID, NTMP_CMD_UPDATE, NTMP_AM_ENTRY_ID);
- err = netc_xmit_ntmp_cmd(user, &cbd);
+ err = netc_xmit_ntmp_cmd(user, &cbd, &swcbd);
if (err)
dev_err(user->dev, "Failed to update RSST entry, err: %pe\n",
ERR_PTR(err));
- ntmp_free_data_mem(&data);
-
return err;
}
EXPORT_SYMBOL_GPL(ntmp_rsst_update_entry);
int ntmp_rsst_query_entry(struct ntmp_user *user, u32 *table, int count)
{
- struct ntmp_dma_buf data = {.dev = user->dev};
struct ntmp_req_by_eid *req;
+ struct netc_swcbd swcbd;
union netc_cbd cbd;
int err, i;
u8 *group;
@@ -425,21 +438,21 @@ int ntmp_rsst_query_entry(struct ntmp_user *user, u32 *table, int count)
/* HW only takes in a full 64 entry table */
return -EINVAL;
- data.size = NTMP_ENTRY_ID_SIZE + RSST_STSE_DATA_SIZE(count) +
- RSST_CFGE_DATA_SIZE(count);
- err = ntmp_alloc_data_mem(&data, (void **)&req);
+ swcbd.size = NTMP_ENTRY_ID_SIZE + RSST_STSE_DATA_SIZE(count) +
+ RSST_CFGE_DATA_SIZE(count);
+ err = ntmp_alloc_data_mem(user->dev, &swcbd, (void **)&req);
if (err)
return err;
/* Set the request data buffer */
ntmp_fill_crd_eid(req, user->tbl.rsst_ver, 0, 0, 0);
- ntmp_fill_request_hdr(&cbd, data.dma, NTMP_LEN(sizeof(*req), data.size),
+ ntmp_fill_request_hdr(&cbd, swcbd.dma, NTMP_LEN(sizeof(*req), swcbd.size),
NTMP_RSST_ID, NTMP_CMD_QUERY, NTMP_AM_ENTRY_ID);
- err = netc_xmit_ntmp_cmd(user, &cbd);
+ err = netc_xmit_ntmp_cmd(user, &cbd, &swcbd);
if (err) {
dev_err(user->dev, "Failed to query RSST entry, err: %pe\n",
ERR_PTR(err));
- goto end;
+ return err;
}
group = (u8 *)req;
@@ -447,10 +460,7 @@ int ntmp_rsst_query_entry(struct ntmp_user *user, u32 *table, int count)
for (i = 0; i < count; i++)
table[i] = group[i];
-end:
- ntmp_free_data_mem(&data);
-
- return err;
+ return 0;
}
EXPORT_SYMBOL_GPL(ntmp_rsst_query_entry);
diff --git a/drivers/net/ethernet/freescale/enetc/ntmp_private.h b/drivers/net/ethernet/freescale/enetc/ntmp_private.h
index 7a53db8740db..5ae6f8b92700 100644
--- a/drivers/net/ethernet/freescale/enetc/ntmp_private.h
+++ b/drivers/net/ethernet/freescale/enetc/ntmp_private.h
@@ -13,6 +13,7 @@
#define NTMP_EID_REQ_LEN 8
#define NETC_CBDR_BD_NUM 256
#define NETC_CBDRCIR_INDEX GENMASK(9, 0)
+#define NETC_CBDR_CLEAN_WORK 16
union netc_cbd {
struct {
@@ -55,13 +56,6 @@ union netc_cbd {
} resp_hdr; /* NTMP Response Message Header Format */
};
-struct ntmp_dma_buf {
- struct device *dev;
- size_t size;
- void *buf;
- dma_addr_t dma;
-};
-
struct ntmp_cmn_req_data {
__le16 update_act;
u8 dbg_opt;
diff --git a/include/linux/fsl/ntmp.h b/include/linux/fsl/ntmp.h
index 916dc4fe7de3..83a449b4d6ec 100644
--- a/include/linux/fsl/ntmp.h
+++ b/include/linux/fsl/ntmp.h
@@ -31,6 +31,12 @@ struct netc_tbl_vers {
u8 rsst_ver;
};
+struct netc_swcbd {
+ void *buf;
+ dma_addr_t dma;
+ size_t size;
+};
+
struct netc_cbdr {
struct device *dev;
struct netc_cbdr_regs regs;
@@ -44,9 +50,10 @@ struct netc_cbdr {
void *addr_base_align;
dma_addr_t dma_base;
dma_addr_t dma_base_align;
+ struct netc_swcbd *swcbd;
/* Serialize the order of command BD ring */
- spinlock_t ring_lock;
+ struct mutex ring_lock;
};
struct ntmp_user {
--
2.34.1
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