init_fp_ctx just initialize the fp/msa context, and own_fp_inatomic
just restore FCSR and 64bit FP regs from it, but miss MSACSR and upper
MSA regs for MSA, so MSACSR and MSA upper regs's value from previous
task on current cpu can leak into current task and cause unpredictable
behavior when MSA context not initialized.
Signed-off-by: Huang Pei <huangpei@xxxxxxxxxxx>
---
arch/mips/kernel/traps.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 38aa07ccdbcc..cf788591f091 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1287,6 +1287,18 @@ static int enable_restore_fp_context(int msa)
err = own_fpu_inatomic(1);
if (msa && !err) {
enable_msa();
+ /*
+ * with MSA enabled, userspace can see MSACSR
+ * and MSA regs, but the values in them are from
+ * other task before current task, restore them
+ * from saved fp/msa context
+ */
+ write_msa_csr(current->thread.fpu.msacsr);
+ /*
+ * own_fpu_inatomic(1) just restore low 64bit,
+ * fix the high 64bit
+ */
+ init_msa_upper();
set_thread_flag(TIF_USEDMSA);
set_thread_flag(TIF_MSA_CTX_LIVE);
}
--
2.17.1
