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. 3. Require callers to hold ring_lock across netc_xmit_ntmp_cmd() netc_xmit_ntmp_cmd() releases the ring_lock before the caller finishes consuming the response. At this point, if a concurrent thread submits a new command, it may trigger ntmp_clean_cbdr() and free the DMA buffer while it is still in use. Move ring_lock ownership to the caller to ensure the response buffer cannot be reclaimed prematurely. So the helpers ntmp_select_and_lock_cbdr() and ntmp_unlock_cbdr() are added. 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 --- drivers/net/ethernet/freescale/enetc/ntmp.c | 214 ++++++++++-------- .../ethernet/freescale/enetc/ntmp_private.h | 8 +- include/linux/fsl/ntmp.h | 9 +- 3 files changed, 134 insertions(+), 97 deletions(-) diff --git a/drivers/net/ethernet/freescale/enetc/ntmp.c b/drivers/net/ethernet/freescale/enetc/ntmp.c index b188eb2d40c0..70bbc5d2d5d4 100644 --- a/drivers/net/ethernet/freescale/enetc/ntmp.c +++ b/drivers/net/ethernet/freescale/enetc/ntmp.c @@ -7,6 +7,7 @@ #include #include #include +#include #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 +78,24 @@ 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) +{ + if (unlikely(!swcbd->buf)) + return; + + 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++) + ntmp_free_data_mem(cbdr->dev, &cbdr->swcbd[i]); + + vfree(cbdr->swcbd); dma_free_coherent(cbdr->dev, cbdr->dma_size, cbdr->addr_base, cbdr->dma_base); memset(cbdr, 0, sizeof(*cbdr)); @@ -94,40 +115,59 @@ 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 void ntmp_select_and_lock_cbdr(struct ntmp_user *user, + struct netc_cbdr **cbdr) +{ + /* Currently only ENETC is supported, and it has only one command + * BD ring. + */ + *cbdr = &user->ring[0]; + + mutex_lock(&(*cbdr)->ring_lock); +} + +static void ntmp_unlock_cbdr(struct netc_cbdr *cbdr) +{ + mutex_unlock(&cbdr->ring_lock); +} + +static int netc_xmit_ntmp_cmd(struct netc_cbdr *cbdr, 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; - /* Currently only i.MX95 ENETC is supported, and it only has one - * command BD ring - */ - cbdr = &user->ring[0]; - - spin_lock_bh(&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))) { + ntmp_free_data_mem(cbdr->dev, swcbd); + return -EBUSY; + } + } 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 */ @@ -135,17 +175,16 @@ 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; + return err; if (unlikely(val & NETC_CBDRCIR_SBE)) { - dev_err(user->dev, "Command BD system bus error\n"); - err = -EIO; - goto cbdr_unlock; + dev_err(cbdr->dev, "Command BD system bus error\n"); + return -EIO; } dma_rmb(); @@ -157,40 +196,29 @@ static int netc_xmit_ntmp_cmd(struct ntmp_user *user, union netc_cbd *cbd) /* Check the writeback error status */ status = le16_to_cpu(cbd->resp_hdr.error_rr) & NTMP_RESP_ERROR; if (unlikely(status)) { - err = -EIO; - dev_err(user->dev, "Command BD error: 0x%04x\n", status); + dev_err(cbdr->dev, "Command BD error: 0x%04x\n", status); + return -EIO; } - ntmp_clean_cbdr(cbdr); - dma_wmb(); - -cbdr_unlock: - spin_unlock_bh(&cbdr->ring_lock); - - return err; + return 0; } -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) @@ -241,37 +269,39 @@ 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; + struct netc_cbdr *cbdr; 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); + ntmp_select_and_lock_cbdr(user, &cbdr); + err = netc_xmit_ntmp_cmd(cbdr, &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); + ntmp_unlock_cbdr(cbdr); 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) +static int ntmp_query_entry_by_id(struct netc_cbdr *cbdr, int tbl_id, + 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; @@ -283,10 +313,11 @@ 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(cbdr, &cbd, swcbd); if (err) { - dev_err(user->dev, + dev_err(cbdr->dev, "Failed to query entry 0x%x of %s, err: %pe\n", entry_id, ntmp_table_name(tbl_id), ERR_PTR(err)); return err; @@ -300,7 +331,7 @@ static int ntmp_query_entry_by_id(struct ntmp_user *user, int tbl_id, resp = (struct ntmp_cmn_resp_query *)req; if (unlikely(le32_to_cpu(resp->entry_id) != entry_id)) { - dev_err(user->dev, + dev_err(cbdr->dev, "%s: query EID 0x%x doesn't match response EID 0x%x\n", ntmp_table_name(tbl_id), entry_id, le32_to_cpu(resp->entry_id)); return -EIO; @@ -312,15 +343,15 @@ 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; + struct netc_cbdr *cbdr; 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; @@ -329,14 +360,15 @@ 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); + + ntmp_select_and_lock_cbdr(user, &cbdr); + err = netc_xmit_ntmp_cmd(cbdr, &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); + ntmp_unlock_cbdr(cbdr); return err; } @@ -345,31 +377,31 @@ 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; + struct netc_cbdr *cbdr; 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); + + ntmp_select_and_lock_cbdr(user, &cbdr); + err = ntmp_query_entry_by_id(cbdr, NTMP_MAFT_ID, req, &swcbd, true); if (err) - goto end; + goto unlock_cbdr; resp = (struct maft_resp_query *)req; maft->keye = resp->keye; maft->cfge = resp->cfge; -end: - ntmp_free_data_mem(&data); +unlock_cbdr: + ntmp_unlock_cbdr(cbdr); return err; } @@ -385,8 +417,9 @@ 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; + struct netc_cbdr *cbdr; union netc_cbd cbd; int err, i; @@ -394,8 +427,8 @@ 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; @@ -405,15 +438,15 @@ 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); + ntmp_select_and_lock_cbdr(user, &cbdr); + err = netc_xmit_ntmp_cmd(cbdr, &cbd, &swcbd); if (err) dev_err(user->dev, "Failed to update RSST entry, err: %pe\n", ERR_PTR(err)); - - ntmp_free_data_mem(&data); + ntmp_unlock_cbdr(cbdr); return err; } @@ -421,8 +454,9 @@ 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; + struct netc_cbdr *cbdr; union netc_cbd cbd; int err, i; u8 *group; @@ -431,21 +465,23 @@ 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); + + ntmp_select_and_lock_cbdr(user, &cbdr); + err = netc_xmit_ntmp_cmd(cbdr, &cbd, &swcbd); if (err) { dev_err(user->dev, "Failed to query RSST entry, err: %pe\n", ERR_PTR(err)); - goto end; + goto unlock_cbdr; } group = (u8 *)req; @@ -453,8 +489,8 @@ 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); +unlock_cbdr: + ntmp_unlock_cbdr(cbdr); return err; } diff --git a/drivers/net/ethernet/freescale/enetc/ntmp_private.h b/drivers/net/ethernet/freescale/enetc/ntmp_private.h index 3459cc45b610..f8dff3ba2c28 100644 --- a/drivers/net/ethernet/freescale/enetc/ntmp_private.h +++ b/drivers/net/ethernet/freescale/enetc/ntmp_private.h @@ -14,6 +14,7 @@ #define NETC_CBDR_BD_NUM 256 #define NETC_CBDRCIR_INDEX GENMASK(9, 0) #define NETC_CBDRCIR_SBE BIT(31) +#define NETC_CBDR_CLEAN_WORK 16 union netc_cbd { struct { @@ -56,13 +57,6 @@ 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