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Message-ID: <CAMkAt6qBTStDyr6_0ca7f2r1UU=P5qFjhO-WWtfnHnH5TsRaSw@mail.gmail.com>
Date: Wed, 17 Nov 2021 19:41:36 -0700
From: Peter Gonda <pgonda@...gle.com>
To: Michael Sterritt <sterritt@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <jroedel@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Tom Lendacky <Thomas.Lendacky@....com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
linux-coco@...ts.linux.dev, marcorr@...gle.com
Subject: Re: [PATCH] Fix SEV-ES INS/OUTS instructions for word, dword, and qword.
On Wed, Nov 17, 2021 at 7:13 PM Michael Sterritt <sterritt@...gle.com> 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.
I think this should include:
Fixes: f980f9c31a923 (x86/sev-es: Compile early handler code into kernel image)
>
> Signed-off-by: Michael Sterritt <sterritt@...gle.com>
> Reviewed-by: Marc Orr <marcorr@...gle.com>
> Reviewed-by: Peter Gonda <pgonda@...gle.com>
> ---
> 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
>
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