From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit 6fcab2791543924d438e7fa49276d0998b0a069f ]
As reported in [1], a platform firmware update that increased the number of method parameters and forgot to update a least one of its callers, caused ACPICA to crash due to use-after-free.
Since this a result of a clear AML issue that arguably cannot be fixed up by the interpreter (it cannot produce missing data out of thin air), address it by making ACPICA refuse to evaluate a method if the caller attempts to pass fewer arguments than expected to it.
Closes: https://github.com/acpica/acpica/issues/1027 [1] Reported-by: Peter Williams peter@newton.cx Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Hans de Goede hansg@kernel.org Tested-by: Hans de Goede hansg@kernel.org # Dell XPS 9640 with BIOS 1.12.0 Link: https://patch.msgid.link/5909446.DvuYhMxLoT@rjwysocki.net Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@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:
## Key Reasons for Backporting:
### 1. **Critical Security Bug - Use-After-Free** The commit message explicitly states this fixes a use-after-free vulnerability that causes ACPICA to crash. Use-after-free bugs are severe security issues that can lead to: - System crashes and denial of service - Potential arbitrary code execution - Memory corruption
### 2. **Real-World Impact** The commit references an actual bug report with a specific hardware/firmware scenario: - Platform firmware update increased method parameters - Firmware forgot to update at least one caller - This caused a real crash on actual hardware (Dell XPS 9640 with BIOS 1.12.0) - The bug has been reported, tested, and verified by multiple people
### 3. **Small, Focused Fix** The code change is minimal and surgical: ```c + if (this_walk_state->num_operands < obj_desc->method.param_count) { + ACPI_ERROR((AE_INFO, "Missing argument for method [%4.4s]", + acpi_ut_get_node_name(method_node))); + + return_ACPI_STATUS(AE_AML_UNINITIALIZED_ARG); + } ``` This adds a simple bounds check before method execution, which is exactly the type of defensive programming that should be in stable kernels.
### 4. **Prevents Memory Corruption** Looking at the surrounding code (specifically line 542 in the original): ```c for (i = 0; i < obj_desc->method.param_count; i++) { acpi_ut_remove_reference(this_walk_state->operands[i]); this_walk_state->operands[i] = NULL; } ``` Without the check, if `num_operands < param_count`, this loop would access beyond the valid operands, causing use-after-free.
### 5. **Clear Error Handling** The fix properly returns `AE_AML_UNINITIALIZED_ARG`, which is an existing ACPICA error code specifically designed for this scenario ("Method tried to use an uninitialized argument"). This maintains API compatibility.
### 6. **No Architectural Changes** The commit: - Doesn't introduce new features - Doesn't change existing behavior for valid code - Only adds validation to prevent crashes from invalid AML - Is confined to the ACPICA subsystem
### 7. **Firmware Bug Mitigation** This is a defensive fix against firmware bugs, which is exactly the type of robustness stable kernels need. The kernel should not crash due to firmware mistakes.
## Comparison with Similar Commits:
Unlike the similar commits shown (which were mostly about improving error messages or cosmetic changes), this commit: - Fixes an actual crash/security issue - Has been reported and tested on real hardware - Prevents memory corruption - Is not just a theoretical improvement
This aligns perfectly with stable kernel rules: important bug fixes with minimal risk that improve system stability and security.
drivers/acpi/acpica/dsmethod.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/acpi/acpica/dsmethod.c b/drivers/acpi/acpica/dsmethod.c index ee1832ba39a24..132ab74935be8 100644 --- a/drivers/acpi/acpica/dsmethod.c +++ b/drivers/acpi/acpica/dsmethod.c @@ -483,6 +483,13 @@ acpi_ds_call_control_method(struct acpi_thread_state *thread, return_ACPI_STATUS(AE_NULL_OBJECT); }
+ if (this_walk_state->num_operands < obj_desc->method.param_count) { + ACPI_ERROR((AE_INFO, "Missing argument for method [%4.4s]", + acpi_ut_get_node_name(method_node))); + + return_ACPI_STATUS(AE_AML_UNINITIALIZED_ARG); + } + /* Init for new method, possibly wait on method mutex */
status =