From: Mark Brown broonie@kernel.org
commit e35ac9d0b56e9efefaeeb84b635ea26c2839ea86 upstream.
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.
Fixes: bc0ee4760364 ("arm64/sve: Core task context handling") Cc: stable@vger.kernel.org # 4.15.x Signed-off-by: Mark Brown broonie@kernel.org Link: https://lore.kernel.org/r/20210909165356.10675-1-broonie@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/fpsimd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -434,7 +434,7 @@ size_t sve_state_size(struct task_struct 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; }