diff options
| author | Lai Jiangshan <laijs@linux.alibaba.com> | 2021-11-26 18:11:22 +0800 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-12-03 19:13:53 +0100 |
| commit | 1367afaa2ee90d1c956dfc224e199fcb3ff3f8cc (patch) | |
| tree | 19d948b14420f3ff5327c15adfea84543e7bd4d2 | |
| parent | c07e45553da1808aa802e9f0ffa8108cfeaf7a17 (diff) | |
x86/entry: Use the correct fence macro after swapgs in kernel CR3
The commit
c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching")
removed a CR3 write in the faulting path of load_gs_index().
But the path's FENCE_SWAPGS_USER_ENTRY has no fence operation if PTI is
enabled, see spectre_v1_select_mitigation().
Rather, it depended on the serializing CR3 write of SWITCH_TO_KERNEL_CR3
and since it got removed, add a FENCE_SWAPGS_KERNEL_ENTRY call to make
sure speculation is blocked.
[ bp: Massage commit message and comment. ]
Fixes: c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211126101209.8613-3-jiangshanlai@gmail.com
| -rw-r--r-- | arch/x86/entry/entry_64.S | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index f1a8b5b2af96..f9e1c06a1c32 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -987,11 +987,6 @@ SYM_CODE_START_LOCAL(error_entry) pushq %r12 ret -.Lerror_entry_done_lfence: - FENCE_SWAPGS_KERNEL_ENTRY -.Lerror_entry_done: - ret - /* * There are two places in the kernel that can potentially fault with * usergs. Handle them here. B stepping K8s sometimes report a @@ -1014,8 +1009,14 @@ SYM_CODE_START_LOCAL(error_entry) * .Lgs_change's error handler with kernel gsbase. */ SWAPGS - FENCE_SWAPGS_USER_ENTRY - jmp .Lerror_entry_done + + /* + * Issue an LFENCE to prevent GS speculation, regardless of whether it is a + * kernel or user gsbase. + */ +.Lerror_entry_done_lfence: + FENCE_SWAPGS_KERNEL_ENTRY + ret .Lbstep_iret: /* Fix truncated RIP */ |