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authorDave Martin <Dave.Martin@arm.com>2017-08-18 16:57:01 +0100
committerWill Deacon <will.deacon@arm.com>2017-08-22 18:15:42 +0100
commit096622104e14d8a1db4860bd557717067a0515d2 (patch)
tree02b14b3fadad8856511053c2c9d70ac92116a11d /arch/arm64/kernel
parentLinux 4.13-rc6 (diff)
downloadlinux-dev-096622104e14d8a1db4860bd557717067a0515d2.tar.xz
linux-dev-096622104e14d8a1db4860bd557717067a0515d2.zip
arm64: fpsimd: Prevent registers leaking across exec
There are some tricky dependencies between the different stages of flushing the FPSIMD register state during exec, and these can race with context switch in ways that can cause the old task's regs to leak across. In particular, a context switch during the memset() can cause some of the task's old FPSIMD registers to reappear. Disabling preemption for this small window would be no big deal for performance: preemption is already disabled for similar scenarios like updating the FPSIMD registers in sigreturn. So, instead of rearranging things in ways that might swap existing subtle bugs for new ones, this patch just disables preemption around the FPSIMD state flushing so that races of this type can't occur here. This brings fpsimd_flush_thread() into line with other code paths. Cc: stable@vger.kernel.org Fixes: 674c242c9323 ("arm64: flush FP/SIMD state correctly after execve()") Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r--arch/arm64/kernel/fpsimd.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 06da8ea16bbe..c7b4995868e1 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -161,9 +161,11 @@ void fpsimd_flush_thread(void)
{
if (!system_supports_fpsimd())
return;
+ preempt_disable();
memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
fpsimd_flush_task_state(current);
set_thread_flag(TIF_FOREIGN_FPSTATE);
+ preempt_enable();
}
/*