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authorJoerg Roedel <jroedel@suse.de>2023-10-16 14:42:50 +0200
committerBorislav Petkov (AMD) <bp@alien8.de>2023-10-17 10:58:16 +0200
commit63e44bc52047f182601e7817da969a105aa1f721 (patch)
tree3a627e7e557da4e8273458595a8483fab82b2fa4
parentb9cb9c45583b911e0db71d09caa6b56469eb2bdf (diff)
x86/sev: Check for user-space IOIO pointing to kernel space
Check the memory operand of INS/OUTS before emulating the instruction. The #VC exception can get raised from user-space, but the memory operand can be manipulated to access kernel memory before the emulation actually begins and after the exception handler has run. [ bp: Massage commit message. ] Fixes: 597cfe48212a ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler") Reported-by: Tom Dohrmann <erbse.13@gmx.de> Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Cc: <stable@kernel.org>
-rw-r--r--arch/x86/boot/compressed/sev.c5
-rw-r--r--arch/x86/kernel/sev-shared.c31
2 files changed, 34 insertions, 2 deletions
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index afd91041ec3e..80d76aea1f7b 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -108,6 +108,11 @@ static enum es_result vc_ioio_check(struct es_em_ctxt *ctxt, u16 port, size_t si
return ES_OK;
}
+static bool fault_in_kernel_space(unsigned long address)
+{
+ return false;
+}
+
#undef __init
#define __init
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index bcd77c48be0a..4d729686f992 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -592,6 +592,23 @@ fail:
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
}
+static enum es_result vc_insn_string_check(struct es_em_ctxt *ctxt,
+ unsigned long address,
+ bool write)
+{
+ if (user_mode(ctxt->regs) && fault_in_kernel_space(address)) {
+ ctxt->fi.vector = X86_TRAP_PF;
+ ctxt->fi.error_code = X86_PF_USER;
+ ctxt->fi.cr2 = address;
+ if (write)
+ ctxt->fi.error_code |= X86_PF_WRITE;
+
+ return ES_EXCEPTION;
+ }
+
+ return ES_OK;
+}
+
static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
void *src, char *buf,
unsigned int data_size,
@@ -599,7 +616,12 @@ static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,
bool backwards)
{
int i, b = backwards ? -1 : 1;
- enum es_result ret = ES_OK;
+ unsigned long address = (unsigned long)src;
+ enum es_result ret;
+
+ ret = vc_insn_string_check(ctxt, address, false);
+ if (ret != ES_OK)
+ return ret;
for (i = 0; i < count; i++) {
void *s = src + (i * data_size * b);
@@ -620,7 +642,12 @@ static enum es_result vc_insn_string_write(struct es_em_ctxt *ctxt,
bool backwards)
{
int i, s = backwards ? -1 : 1;
- enum es_result ret = ES_OK;
+ unsigned long address = (unsigned long)dst;
+ enum es_result ret;
+
+ ret = vc_insn_string_check(ctxt, address, true);
+ if (ret != ES_OK)
+ return ret;
for (i = 0; i < count; i++) {
void *d = dst + (i * data_size * s);