[PATCH] arm64/sme: Always exit sme_alloc() early with existing storage

[Mark Brown]

When sme_alloc() is called with existing storage and we are not flushing we
will always allocate new storage, both leaking the existing storage and
corrupting the state. Fix this by separating the checks for flushing and
for existing storage as we do for SVE.

Callers that reallocate (eg, due to changing the vector length) should
call sme_free() themselves.

Fixes: 5d0a8d2fba50 (arm64/ptrace: Ensure that SME is set up for target when writing SSVE state)
Signed-off-by: Mark Brown <broonie at kernel.org>
Cc:  <stable at vger.kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 1559c706d32d..7363f2eb98e8 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1245,8 +1245,10 @@ void fpsimd_release_task(struct task_struct *dead_task)
  */
 void sme_alloc(struct task_struct *task, bool flush)
 {
-	if (task->thread.sme_state && flush) {
-		memset(task->thread.sme_state, 0, sme_state_size(task));
+	if (task->thread.sme_state) {
+		if (flush)
+			memset(task->thread.sme_state, 0,
+			       sme_state_size(task));
 		return;
 	}
 

---
base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a
change-id: 20240112-arm64-sme-flush-09bdc40bb4fc

Best regards,
-- 
Mark Brown <broonie at kernel.org>