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From: "tip-bot2 for Lai Jiangshan" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Lai Jiangshan <laijs@linux.alibaba.com>,
	Borislav Petkov <bp@suse.de>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/urgent] x86/entry: Use the correct fence macro after swapgs in kernel CR3
Date: Sat, 04 Dec 2021 11:45:26 -0000	[thread overview]
Message-ID: <163861832657.11128.14542109186341632803.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20211126101209.8613-3-jiangshanlai@gmail.com>

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     1367afaa2ee90d1c956dfc224e199fcb3ff3f8cc
Gitweb:        https://git.kernel.org/tip/1367afaa2ee90d1c956dfc224e199fcb3ff3f8cc
Author:        Lai Jiangshan <laijs@linux.alibaba.com>
AuthorDate:    Fri, 26 Nov 2021 18:11:22 +08:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 03 Dec 2021 19:13:53 +01:00

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
---
 arch/x86/entry/entry_64.S | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f1a8b5b..f9e1c06 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 */

  reply	other threads:[~2021-12-04 11:45 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-26 10:11 [PATCH V6 00/49] x86/entry/64: Convert a bunch of ASM entry code into C code Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 01/49] x86/entry: Add fence for kernel entry swapgs in paranoid_entry() Lai Jiangshan
2021-12-04 11:45   ` [tip: x86/urgent] x86/entry: Add a fence for kernel entry SWAPGS " tip-bot2 for Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 02/49] x86/entry: Use the correct fence macro after swapgs in kernel CR3 Lai Jiangshan
2021-12-04 11:45   ` tip-bot2 for Lai Jiangshan [this message]
2021-11-26 10:11 ` [PATCH V6 03/49] x86/xen: Add xenpv_restore_regs_and_return_to_usermode() Lai Jiangshan
2021-12-04 11:45   ` [tip: x86/urgent] " tip-bot2 for Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 04/49] x86/entry: Use swapgs and native_iret directly in swapgs_restore_regs_and_return_to_usermode Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 05/49] compiler_types.h: Add __noinstr_section() for noinstr Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 06/49] x86/entry: Introduce __entry_text for entry code written in C Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 07/49] x86/entry: Move PTI_USER_* to arch/x86/include/asm/processor-flags.h Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 08/49] x86: Remove unused kernel_to_user_p4dp() and user_to_kernel_p4dp() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 09/49] x86: Replace PTI_PGTABLE_SWITCH_BIT with PTI_USER_PGTABLE_BIT Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 10/49] x86: Mark __native_read_cr3() & native_write_cr3() as __always_inline Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 11/49] x86/traps: Move the declaration of native_irq_return_iret into proto.h Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 12/49] x86/entry: Add arch/x86/entry/entry64.c for C entry code Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 13/49] x86/entry: Expose the address of .Lgs_change to entry64.c Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 14/49] x86/entry: Add C verion of SWITCH_TO_KERNEL_CR3 as switch_to_kernel_cr3() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 15/49] x86/traps: Add fence_swapgs_{user,kernel}_entry() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 16/49] x86/entry: Add C user_entry_swapgs_and_fence() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 17/49] x86/traps: Move pt_regs only in fixup_bad_iret() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 18/49] x86/entry: Switch the stack after error_entry() returns Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 19/49] x86/entry: move PUSH_AND_CLEAR_REGS out of error_entry Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 20/49] x86/entry: Move cld to the start of idtentry Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 21/49] x86/entry: Don't call error_entry for XENPV Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 22/49] x86/entry: Convert SWAPGS to swapgs in error_entry() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 23/49] x86/entry: Implement the whole error_entry() as C code Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 24/49] x86/entry: Use idtentry macro for entry_INT80_compat Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 25/49] x86/entry: Convert SWAPGS to swapgs in entry_SYSENTER_compat() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 26/49] x86: Remove the definition of SWAPGS Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 27/49] x86/entry: Make paranoid_exit() callable Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 28/49] x86/entry: Call paranoid_exit() in asm_exc_nmi() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 29/49] x86/entry: move PUSH_AND_CLEAR_REGS out of paranoid_entry Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 30/49] x86/entry: Add the C version ist_switch_to_kernel_cr3() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 31/49] x86/entry: Skip CR3 write when the saved CR3 is kernel CR3 in RESTORE_CR3 Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 32/49] x86/entry: Add the C version ist_restore_cr3() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 33/49] x86/entry: Add the C version get_percpu_base() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 34/49] x86/entry: Add the C version ist_switch_to_kernel_gsbase() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 35/49] x86/entry: Implement the C version ist_paranoid_entry() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 36/49] x86/entry: Implement the C version ist_paranoid_exit() Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 37/49] x86/entry: Add a C macro to define the function body for IST in .entry.text Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 38/49] x86/debug, mce: Use C entry code Lai Jiangshan
2021-11-26 10:11 ` [PATCH V6 39/49] x86/idtentry.h: Move the definitions *IDTENTRY_{MCE|DEBUG}* up Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 40/49] x86/nmi: Use DEFINE_IDTENTRY_NMI for nmi Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 41/49] x86/nmi: Use C entry code Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 42/49] x86/entry: Add a C macro to define the function body for IST in .entry.text with an error code Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 43/49] x86/doublefault: Use C entry code Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 44/49] x86/sev: Add and use ist_vc_switch_off_ist() Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 45/49] x86/sev: Use C entry code Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 46/49] x86/entry: Remove ASM function paranoid_entry() and paranoid_exit() Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 47/49] x86/entry: Remove the unused ASM macros Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 48/49] x86/entry: Remove save_ret from PUSH_AND_CLEAR_REGS Lai Jiangshan
2021-11-26 10:12 ` [PATCH V6 49/49] x86/syscall/64: Move the checking for sysret to C code Lai Jiangshan
2021-11-27 17:46 ` [PATCH V6 00/49] x86/entry/64: Convert a bunch of ASM entry code into " Damian Tometzki
2021-12-03  9:31 ` Lai Jiangshan
2021-12-03  9:39   ` Borislav Petkov
2021-12-03 10:10     ` Lai Jiangshan
2021-12-03 10:18       ` Borislav Petkov

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