From: Will Deacon Date: Tue, 14 Nov 2017 14:33:28 +0000 (+0000) Subject: arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks X-Git-Tag: Ubuntu-4.13.0-37.42~61 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=a8742fd582a7ff4c5cceae7572a0f182c79164cb;p=mirror_ubuntu-artful-kernel.git arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks Commit 18011eac28c7 upstream. When unmapping the kernel at EL0, we use tpidrro_el0 as a scratch register during exception entry from native tasks and subsequently zero it in the kernel_ventry macro. We can therefore avoid zeroing tpidrro_el0 in the context-switch path for native tasks using the entry trampoline. Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon Signed-off-by: Ard Biesheuvel Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 2843ade2dad2249900f508f61068d245921ce9f1) CVE-2017-5753 CVE-2017-5715 CVE-2017-5754 Signed-off-by: Paolo Pisati Acked-by: Brad Figg Acked-by: Kleber Sacilotto de Souza Acked-by: Thadeu Lima de Souza Cascardo Signed-off-by: Kleber Sacilotto de Souza --- diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index e6bf19c1dddb..ccf536f53bdb 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -305,16 +305,14 @@ void tls_preserve_current_state(void) static void tls_thread_switch(struct task_struct *next) { - unsigned long tpidr, tpidrro; - tls_preserve_current_state(); - tpidr = *task_user_tls(next); - tpidrro = is_compat_thread(task_thread_info(next)) ? - next->thread.tp_value : 0; + if (is_compat_thread(task_thread_info(next))) + write_sysreg(next->thread.tp_value, tpidrro_el0); + else if (!arm64_kernel_unmapped_at_el0()) + write_sysreg(0, tpidrro_el0); - write_sysreg(tpidr, tpidr_el0); - write_sysreg(tpidrro, tpidrro_el0); + write_sysreg(*task_user_tls(next), tpidr_el0); } /* Restore the UAO state depending on next's addr_limit */