From: Miri Korenblit miriam.rachel.korenblit@intel.com
[ Upstream commit 1cc2c48c4af81bed5ddbe9f2c9d6e20fa163acf9 ]
rxq->read is accessed without the rxq->lock in a few places, Make sure to have the lock there.
Signed-off-by: Miri Korenblit miriam.rachel.korenblit@intel.com Reviewed-by: Emmanuel Grumbach emmanuel.grumbach@intel.com Tested-by: Emmanuel Grumbach emmanuel.grumbach@intel.com Link: https://patch.msgid.link/20250424153620.73725f207aaa.I1a3e4b6c5fd370e029fdac... Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Sasha Levin sashal@kernel.org ---
Based on my analysis of the commit and the surrounding code, here is my assessment: ## YES This commit should be backported to stable kernel trees. ### Analysis: **1. Race Condition Fix:** The commit fixes a clear race condition where `rxq->read` is accessed without proper locking in two functions: - `iwl_dbgfs_rx_queue_read()` - a debugfs read function - `iwl_trans_pcie_dump_data()` - a function that calculates buffer sizes for error dumps **2. Specific Code Changes:** - In `iwl_dbgfs_rx_queue_read()`, the commit adds `spin_lock_bh(&rxq->lock)` before accessing `rxq->read` and `spin_unlock_bh(&rxq->lock)` after finishing with all rxq fields - In `iwl_trans_pcie_dump_data()`, it adds the same locking around the calculation `num_rbs = (num_rbs - rxq->read) & RX_QUEUE_MASK` **3. Why This Needs Backporting:** **Race Condition Impact:** Looking at the rx.c code, `rxq->read` is modified in the hot path interrupt handling code (`iwl_pcie_irq_rx_handler`) under `spin_lock(&rxq->lock)`. The unlocked access in the debugfs and dump functions can lead to: - Reading inconsistent values during updates - Potential crashes if the read occurs during structure modifications - Incorrect debug information or dump calculations **Similarity to Backported Commits:** This follows the exact same pattern as Similar Commit #1 and #3, which were both marked as "YES" for backporting. Both dealt with missing locking for shared data structures in the iwlwifi driver. **4. Backport Criteria Assessment:** - ✅ **Fixes a bug affecting users:** Race conditions can cause system instability - ✅ **Small and contained fix:** Only adds proper locking, minimal code change - ✅ **No major architectural changes:** Just adds missing synchronization - ✅ **Minimal risk of regression:** Standard locking pattern already used elsewhere - ✅ **Confined to iwlwifi subsystem:** Changes are local to Intel WiFi driver **5. Risk Assessment:** The fix is extremely low risk - it simply adds the missing locking that should have been there originally. The locking pattern (`spin_lock_bh`/`spin_unlock_bh`) is already used extensively throughout the same file for protecting rxq access. This is a textbook stable tree candidate: it fixes a real concurrency bug with minimal, safe code changes that follow existing patterns in the codebase.
drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c index e9807fcca6ad1..5c2e8d2883976 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c @@ -2701,6 +2701,8 @@ static ssize_t iwl_dbgfs_rx_queue_read(struct file *file, for (i = 0; i < trans->num_rx_queues && pos < bufsz; i++) { struct iwl_rxq *rxq = &trans_pcie->rxq[i];
+ spin_lock_bh(&rxq->lock); + pos += scnprintf(buf + pos, bufsz - pos, "queue#: %2d\n", i); pos += scnprintf(buf + pos, bufsz - pos, "\tread: %u\n", @@ -2721,6 +2723,7 @@ static ssize_t iwl_dbgfs_rx_queue_read(struct file *file, pos += scnprintf(buf + pos, bufsz - pos, "\tclosed_rb_num: Not Allocated\n"); } + spin_unlock_bh(&rxq->lock); } ret = simple_read_from_buffer(user_buf, count, ppos, buf, pos); kfree(buf); @@ -3385,8 +3388,11 @@ iwl_trans_pcie_dump_data(struct iwl_trans *trans, /* Dump RBs is supported only for pre-9000 devices (1 queue) */ struct iwl_rxq *rxq = &trans_pcie->rxq[0]; /* RBs */ + spin_lock_bh(&rxq->lock); num_rbs = iwl_get_closed_rb_stts(trans, rxq); num_rbs = (num_rbs - rxq->read) & RX_QUEUE_MASK; + spin_unlock_bh(&rxq->lock); + len += num_rbs * (sizeof(*data) + sizeof(struct iwl_fw_error_dump_rb) + (PAGE_SIZE << trans_pcie->rx_page_order));