From: Kyungwook Boo bookyungwook@gmail.com
[ Upstream commit 015bac5daca978448f2671478c553ce1f300c21e ]
When the device sends a specific input, an integer underflow can occur, leading to MMIO write access to an invalid page.
Prevent the integer underflow by changing the type of related variables.
Signed-off-by: Kyungwook Boo bookyungwook@gmail.com Link: https://lore.kernel.org/lkml/ffc91764-1142-4ba2-91b6-8c773f6f7095@gmail.com/... Reviewed-by: Przemek Kitszel przemyslaw.kitszel@intel.com Reviewed-by: Simon Horman horms@kernel.org Reviewed-by: Aleksandr Loktionov aleksandr.loktionov@intel.com Tested-by: Rinitha S sx.rinitha@intel.com (A Contingent worker at Intel) Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: Sasha Levin sashal@kernel.org ---
**YES** This commit should be backported to stable kernel trees. Here's my extensive analysis: ## Analysis of Code Changes The commit changes variable types in `i40e_clear_hw()` from unsigned (`u32`) to signed (`s32`) for: 1. `num_pf_int` - number of PF interrupts 2. `num_vf_int` - number of VF interrupts 3. `i` - loop counter variable **Critical Security Issue**: The problem occurs when hardware registers contain malicious values where `num_pf_int` or `num_vf_int` could be 0 or 1. In the loops at lines 852-853 and 858-859: ```c for (i = 0; i < num_pf_int - 2; i++) wr32(hw, I40E_PFINT_DYN_CTLN(i), val); ``` If `num_pf_int` is 0 or 1, then `num_pf_int - 2` becomes a large positive number due to unsigned integer underflow (0xFFFFFFFE or 0xFFFFFFFF), causing the loop to iterate billions of times and write to invalid MMIO addresses, leading to system crashes or potential security vulnerabilities. ## Comparison with Similar Commits This fix follows the **exact same pattern** as Similar Commit #2 (fc6f716a5069), which was marked **YES** for backporting. That commit addressed the same class of vulnerability in the same function: - **Similar Commit #2**: Added bounds checking (`j
= base_queue`, `j >= i`) to prevent underflow in queue/VF calculations
- **Current Commit**: Changes variable types to signed to prevent underflow in interrupt calculations Both fixes address **integer underflow vulnerabilities in `i40e_clear_hw()`** that can lead to **MMIO writes to invalid memory pages**. ## Backport Suitability Criteria ✅ **Fixes important security bug**: Prevents system crashes and potential memory corruption ✅ **Small, contained change**: Only changes variable types, no logic changes ✅ **Minimal side effects**: Type changes are safe and don't affect functionality ✅ **No architectural changes**: Simple type fix ✅ **Critical subsystem**: Network driver, but change is isolated ✅ **Clear commit message**: Explicitly describes the security issue ✅ **Follows stable rules**: Important security bugfix with minimal risk ## Historical Context The vulnerability was introduced in commit 838d41d92a90 ("i40e: clear all queues and interrupts") from 2014. A related fix (fc6f716a5069) was already applied for similar underflow issues in the same function and was backported. This commit completes the fix by addressing the remaining underflow vectors. ## Risk Assessment **Risk: MINIMAL** - This is a simple type change that: - Makes signed arithmetic behave correctly - Prevents undefined behavior from unsigned underflow - Has no functional impact on normal operation - Only affects error conditions with malformed hardware registers The fix is **essential for security** and has **virtually zero regression risk**, making it an ideal candidate for stable backporting.
drivers/net/ethernet/intel/i40e/i40e_common.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_common.c b/drivers/net/ethernet/intel/i40e/i40e_common.c index 99dd8187476ba..fe8e6db53f23b 100644 --- a/drivers/net/ethernet/intel/i40e/i40e_common.c +++ b/drivers/net/ethernet/intel/i40e/i40e_common.c @@ -1061,10 +1061,11 @@ int i40e_pf_reset(struct i40e_hw *hw) void i40e_clear_hw(struct i40e_hw *hw) { u32 num_queues, base_queue; - u32 num_pf_int; - u32 num_vf_int; + s32 num_pf_int; + s32 num_vf_int; u32 num_vfs; - u32 i, j; + s32 i; + u32 j; u32 val; u32 eol = 0x7ff;