This is a note to let you know that I've just added the patch titled MIPS: add missing MSACSR and upper MSA initialization to the 5.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mips-add-missing-msacsr-and-upper-msa-initialization.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a29691825fe7fc6727e3dd1fcdbffb98da73a5ef Author: Huang Pei <huangpei@xxxxxxxxxxx> Date: Tue Sep 1 14:53:09 2020 +0800 MIPS: add missing MSACSR and upper MSA initialization [ Upstream commit bb06748207cfb1502d11b90325eba7f8c44c9f02 ] In cc97ab235f3f ("MIPS: Simplify FP context initialization), 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. Fixes: cc97ab235f3f ("MIPS: Simplify FP context initialization") Signed-off-by: Huang Pei <huangpei@xxxxxxxxxxx> Signed-off-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index e664d8b43e72b..2e9d0637591c9 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -1286,6 +1286,18 @@ 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); }