diff options
| author | Borislav Petkov <bp@suse.de> | 2020-04-19 09:59:03 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-24 07:57:20 +0200 |
| commit | 58fb3c3589820cd81b4964757b1196da070e7743 (patch) | |
| tree | 898b2262c2fcc493b844631b64dd53f65e7bad44 | |
| parent | 5706d13e270a64902dbd0729718aff81f8f3b9d4 (diff) | |
x86/mitigations: Clear CPU buffers on the SYSCALL fast path
The fast SYSCALL exit path returns with SYSRET to userspace after
verifying that there's no pending work. MDS mitigation mandates that CPU
buffers must be cleared on transition from kernel to userspace so do
that here too.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/entry/entry_64.S | 2 | ||||
| -rw-r--r-- | arch/x86/include/asm/spec-ctrl.h | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 5 |
3 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index afb805b0148b..6b505d91cac5 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -218,6 +218,8 @@ entry_SYSCALL_64_fastpath: testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jnz int_ret_from_sys_call_irqs_off /* Go to the slow path */ + call mds_user_clear_buffers + movq RIP(%rsp), %rcx movq EFLAGS(%rsp), %r11 RESTORE_C_REGS_EXCEPT_RCX_R11 diff --git a/arch/x86/include/asm/spec-ctrl.h b/arch/x86/include/asm/spec-ctrl.h index 5393babc0598..4a7acb4adc6b 100644 --- a/arch/x86/include/asm/spec-ctrl.h +++ b/arch/x86/include/asm/spec-ctrl.h @@ -85,4 +85,6 @@ static inline void speculative_store_bypass_ht_init(void) { } extern void speculation_ctrl_update(unsigned long tif); extern void speculation_ctrl_update_current(void); +extern void mds_user_clear_buffers(void); + #endif diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index e9aa50ba4f97..950e6bb21955 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -263,6 +263,11 @@ static int __init mds_cmdline(char *str) } early_param("mds", mds_cmdline); +void mds_user_clear_buffers(void) +{ + mds_user_clear_cpu_buffers(); +} + #undef pr_fmt #define pr_fmt(fmt) "TAA: " fmt |