From a4544831370618cb3627e27ffcc27d1cc857868f Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 15 Dec 2017 16:07:22 +0000 Subject: arm64: fpsimd: Fix copying of FP state from signal frame into task struct Commit 9de52a755cfb6da5 ("arm64: fpsimd: Fix failure to restore FPSIMD state after signals") fixed an issue reported in our FPSIMD signal restore code but inadvertently introduced another issue which tends to manifest as random SEGVs in userspace. The problem is that when we copy the struct fpsimd_state from the kernel stack (populated from the signal frame) into the struct held in the current thread_struct, we blindly copy uninitialised stack into the "cpu" field, which means that context-switching of the FP registers is no longer reliable. This patch fixes the problem by copying only the user_fpsimd member of struct fpsimd_state. We should really rework the function prototypes to take struct user_fpsimd_state * instead, but let's just get this fixed for now. Cc: Dave Martin Fixes: 9de52a755cfb6da5 ("arm64: fpsimd: Fix failure to restore FPSIMD state after signals") Reported-by: Geert Uytterhoeven Signed-off-by: Will Deacon --- arch/arm64/kernel/fpsimd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 540a1e010eb5..fae81f7964b4 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1043,7 +1043,7 @@ void fpsimd_update_current_state(struct fpsimd_state *state) local_bh_disable(); - current->thread.fpsimd_state = *state; + current->thread.fpsimd_state.user_fpsimd = state->user_fpsimd; if (system_supports_sve() && test_thread_flag(TIF_SVE)) fpsimd_to_sve(current); -- cgit v1.2.3