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

commit dc7eb8755797ed41a0d1b5c0c39df3c8f401b3d9 upstream.

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@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20240115-arm64-sme-flush-v1-1-7472bd3459b7@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 91e44ac7150f90088f455ad822a08897483d7a7b..f9b3adebcb1870717a8fa01d7251f0fb4413c495 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1280,8 +1280,10 @@ 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;
        }