arm64/sve: Use correct size when reinitialising SVE state
Subsystems (2)
PATCH 1/1 arm64/sve: Use correct size when reinitialising SVE state
When we need a buffer for SVE register state we call sve_alloc() to make sure that one is there. In order to avoid repeated allocations and frees we keep the buffer around unless we change vector length and just memset() it to ensure a clean register state. The function that deals with this takes the task to operate on as an argument, however in the case where we do a memset() we initialise using the SVE state size for the current task rather than the task passed as an argument.
This is only an issue in the case where we are setting the register state for a task via ptrace and the task being configured has a different vector length to the task tracing it. In the case where the buffer is larger in the traced process we will leak old state from the traced process to itself, in the case where the buffer is smaller in the traced process we will overflow the buffer and corrupt memory.
--- arch/arm64/kernel/fpsimd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/kernel/fpsimd.c +1 -1
@@ -513,7 +513,7 @@ size_t sve_state_size(struct task_struct const *task)void sve_alloc (struct task_struct *task) {if (task->thread.sve_state) { -memset (task->thread.sve_state,0 ,sve_state_size (current)); +memset (task->thread.sve_state,0 ,sve_state_size (task));return ; }
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2.20.1
Quoted 9 lines · Mark Brown
When we need a buffer for SVE register state we call
sve_alloc()to make sure that one is there. In order to avoid repeated allocations and frees we keep the buffer around unless we change vector length and justmemset()it to ensure a clean register state. The function that deals with this takes the task to operate on as an argument, however in the case where we do amemset()we initialise using the SVE state size for the current task rather than the task passed as an argument.[...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64/sve: Use correct size when reinitialising SVE state
https://git.kernel.org/arm64/c/e35ac9d0b56e
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