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* [PATCH v2] x86/sev-es: Fix SEV-ES INS/OUTS instructions for word, dword, and qword
@ 2021-11-19 23:27 Michael Sterritt
  2021-11-24 13:28 ` Joerg Roedel
  0 siblings, 1 reply; 2+ messages in thread
From: Michael Sterritt @ 2021-11-19 23:27 UTC (permalink / raw)
  To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
	H. Peter Anvin, Joerg Roedel, Peter Zijlstra, Tom Lendacky,
	linux-kernel, kvm, virtualization, linux-coco, Paolo Bonzini
  Cc: marcorr, pgonda, Michael Sterritt

Properly type the operands being passed to __put_user()/__get_user().
Otherwise, these routines truncate data for dependent instructions
(e.g., INSW) and only read/write one byte.

Tested: Tested by sending a string with `REP OUTSW` to a port and then
reading it back in with `REP INSW` on the same port. Previous behavior
was to only send and receive the first char of the size. For example,
word operations for "abcd" would only read/write "ac". With change, the
full string is now written and read back.

Fixes: f980f9c31a923 (x86/sev-es: Compile early handler code into kernel image)
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Marc Orr <marcorr@google.com>
Reviewed-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Michael Sterritt <sterritt@google.com>
---
v1 -> v2
* Changes subject
* Added fixes tag
* Added Paolo's reviewed-by
 arch/x86/kernel/sev.c | 57 +++++++++++++++++++++++++++++--------------
 1 file changed, 39 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 74f0ec955384..a9fc2ac7a8bd 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -294,11 +294,6 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
 				   char *dst, char *buf, size_t size)
 {
 	unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;
-	char __user *target = (char __user *)dst;
-	u64 d8;
-	u32 d4;
-	u16 d2;
-	u8  d1;
 
 	/*
 	 * This function uses __put_user() independent of whether kernel or user
@@ -320,26 +315,42 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
 	 * instructions here would cause infinite nesting.
 	 */
 	switch (size) {
-	case 1:
+	case 1: {
+		u8 d1;
+		u8 __user *target = (u8 __user *)dst;
+
 		memcpy(&d1, buf, 1);
 		if (__put_user(d1, target))
 			goto fault;
 		break;
-	case 2:
+	}
+	case 2: {
+		u16 d2;
+		u16 __user *target = (u16 __user *)dst;
+
 		memcpy(&d2, buf, 2);
 		if (__put_user(d2, target))
 			goto fault;
 		break;
-	case 4:
+	}
+	case 4: {
+		u32 d4;
+		u32 __user *target = (u32 __user *)dst;
+
 		memcpy(&d4, buf, 4);
 		if (__put_user(d4, target))
 			goto fault;
 		break;
-	case 8:
+	}
+	case 8: {
+		u64 d8;
+		u64 __user *target = (u64 __user *)dst;
+
 		memcpy(&d8, buf, 8);
 		if (__put_user(d8, target))
 			goto fault;
 		break;
+	}
 	default:
 		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
 		return ES_UNSUPPORTED;
@@ -362,11 +373,6 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 				  char *src, char *buf, size_t size)
 {
 	unsigned long error_code = X86_PF_PROT;
-	char __user *s = (char __user *)src;
-	u64 d8;
-	u32 d4;
-	u16 d2;
-	u8  d1;
 
 	/*
 	 * This function uses __get_user() independent of whether kernel or user
@@ -388,26 +394,41 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 	 * instructions here would cause infinite nesting.
 	 */
 	switch (size) {
-	case 1:
+	case 1: {
+		u8 d1;
+		u8 __user *s = (u8 __user *)src;
+
 		if (__get_user(d1, s))
 			goto fault;
 		memcpy(buf, &d1, 1);
 		break;
-	case 2:
+	}
+	case 2: {
+		u16 d2;
+		u16 __user *s = (u16 __user *)src;
+
 		if (__get_user(d2, s))
 			goto fault;
 		memcpy(buf, &d2, 2);
 		break;
-	case 4:
+	}
+	case 4: {
+		u32 d4;
+		u32 __user *s = (u32 __user *)src;
+
 		if (__get_user(d4, s))
 			goto fault;
 		memcpy(buf, &d4, 4);
 		break;
-	case 8:
+	}
+	case 8: {
+		u64 d8;
+		u64 __user *s = (u64 __user *)src;
 		if (__get_user(d8, s))
 			goto fault;
 		memcpy(buf, &d8, 8);
 		break;
+	}
 	default:
 		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
 		return ES_UNSUPPORTED;
-- 
2.34.0.rc2.393.gf8c9666880-goog


^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH v2] x86/sev-es: Fix SEV-ES INS/OUTS instructions for word, dword, and qword
  2021-11-19 23:27 [PATCH v2] x86/sev-es: Fix SEV-ES INS/OUTS instructions for word, dword, and qword Michael Sterritt
@ 2021-11-24 13:28 ` Joerg Roedel
  0 siblings, 0 replies; 2+ messages in thread
From: Joerg Roedel @ 2021-11-24 13:28 UTC (permalink / raw)
  To: Michael Sterritt
  Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
	H. Peter Anvin, Peter Zijlstra, Tom Lendacky, linux-kernel, kvm,
	virtualization, linux-coco, Paolo Bonzini, marcorr, pgonda

On Fri, Nov 19, 2021 at 03:27:57PM -0800, Michael Sterritt wrote:
> Properly type the operands being passed to __put_user()/__get_user().
> Otherwise, these routines truncate data for dependent instructions
> (e.g., INSW) and only read/write one byte.
> 
> Tested: Tested by sending a string with `REP OUTSW` to a port and then
> reading it back in with `REP INSW` on the same port. Previous behavior
> was to only send and receive the first char of the size. For example,
> word operations for "abcd" would only read/write "ac". With change, the
> full string is now written and read back.
> 
> Fixes: f980f9c31a923 (x86/sev-es: Compile early handler code into kernel image)
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Marc Orr <marcorr@google.com>
> Reviewed-by: Peter Gonda <pgonda@google.com>
> Signed-off-by: Michael Sterritt <sterritt@google.com>

Reviewed-by: Joerg Roedel <jroedel@suse.de>


^ permalink raw reply	[flat|nested] 2+ messages in thread

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