Skip to content

L
linux
Commit 74b0a4b9 authored by Nadav Amit's avatar Nadav Amit Committed by Jiri Slaby
Browse files
Options

KVM: x86: Handle errors when RIP is set during far jumps 

commit d1442d85 upstream.

Far jmp/call/ret may fault while loading a new RIP.  Currently KVM does not
handle this case, and may result in failed vm-entry once the assignment is
done.  The tricky part of doing so is that loading the new CS affects the
VMCS/VMCB state, so if we fail during loading the new RIP, we are left in
unconsistent state.  Therefore, this patch saves on 64-bit the old CS
descriptor and restores it if loading RIP failed.
Signed-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarBruce Rogers <brogers@suse.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
parent 293e0568
Hide whitespace changes
Inline Side-by-side
Showing with 77 additions and 36 deletions
arch/x86/kvm/emulate.c
View file @ 74b0a4b9
......@@ -1443,7 +1443,8 @@ static int write_segment_descriptor(struct x86_emulate_ctxt *ctxt,
/* Does not support long mode */
static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
u16 selector, int seg)
u16 selector, int seg,
struct desc_struct *desc)
{
struct desc_struct seg_desc, old_desc;
u8 dpl, rpl, cpl;
......@@ -1570,6 +1571,8 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
}
load:
ctxt->ops->set_segment(ctxt, selector, &seg_desc, 0, seg);
if (desc)
*desc = seg_desc;
return X86EMUL_CONTINUE;
exception:
emulate_exception(ctxt, err_vec, err_code, true);
......@@ -1776,7 +1779,7 @@ static int em_pop_sreg(struct x86_emulate_ctxt *ctxt)
if (rc != X86EMUL_CONTINUE)
return rc;
rc = load_segment_descriptor(ctxt, (u16)selector, seg);
rc = load_segment_descriptor(ctxt, (u16)selector, seg, NULL);
return rc;
}
......@@ -1865,7 +1868,7 @@ static int __emulate_int_real(struct x86_emulate_ctxt *ctxt, int irq)
if (rc != X86EMUL_CONTINUE)
return rc;
rc = load_segment_descriptor(ctxt, cs, VCPU_SREG_CS);
rc = load_segment_descriptor(ctxt, cs, VCPU_SREG_CS, NULL);
if (rc != X86EMUL_CONTINUE)
return rc;
......@@ -1931,7 +1934,7 @@ static int emulate_iret_real(struct x86_emulate_ctxt *ctxt)
if (rc != X86EMUL_CONTINUE)
return rc;
rc = load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS);
rc = load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, NULL);
if (rc != X86EMUL_CONTINUE)
return rc;
......@@ -1970,17 +1973,29 @@ static int em_iret(struct x86_emulate_ctxt *ctxt)
static int em_jmp_far(struct x86_emulate_ctxt *ctxt)
{
int rc;
unsigned short sel;
unsigned short sel, old_sel;
struct desc_struct old_desc, new_desc;
const struct x86_emulate_ops *ops = ctxt->ops;
/* Assignment of RIP may only fail in 64-bit mode */
if (ctxt->mode == X86EMUL_MODE_PROT64)
ops->get_segment(ctxt, &old_sel, &old_desc, NULL,
VCPU_SREG_CS);
memcpy(&sel, ctxt->src.valptr + ctxt->op_bytes, 2);
rc = load_segment_descriptor(ctxt, sel, VCPU_SREG_CS);
rc = load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, &new_desc);
if (rc != X86EMUL_CONTINUE)
return rc;
ctxt->_eip = 0;
memcpy(&ctxt->_eip, ctxt->src.valptr, ctxt->op_bytes);
return X86EMUL_CONTINUE;
rc = assign_eip_far(ctxt, ctxt->src.val, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
/* assigning eip failed; restore the old cs */
ops->set_segment(ctxt, old_sel, &old_desc, 0, VCPU_SREG_CS);
return rc;
}
return rc;
}
static int em_grp45(struct x86_emulate_ctxt *ctxt)
......@@ -2044,21 +2059,33 @@ static int em_ret(struct x86_emulate_ctxt *ctxt)
static int em_ret_far(struct x86_emulate_ctxt *ctxt)
{
int rc;
unsigned long cs;
unsigned long eip, cs;
u16 old_cs;
int cpl = ctxt->ops->cpl(ctxt);
struct desc_struct old_desc, new_desc;
const struct x86_emulate_ops *ops = ctxt->ops;
if (ctxt->mode == X86EMUL_MODE_PROT64)
ops->get_segment(ctxt, &old_cs, &old_desc, NULL,
VCPU_SREG_CS);
rc = emulate_pop(ctxt, &ctxt->_eip, ctxt->op_bytes);
rc = emulate_pop(ctxt, &eip, ctxt->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
if (ctxt->op_bytes == 4)
ctxt->_eip = (u32)ctxt->_eip;
rc = emulate_pop(ctxt, &cs, ctxt->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
/* Outer-privilege level return is not implemented */
if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl)
return X86EMUL_UNHANDLEABLE;
rc = load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS);
rc = load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, &new_desc);
if (rc != X86EMUL_CONTINUE)
return rc;
rc = assign_eip_far(ctxt, eip, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS);
}
return rc;
}
......@@ -2099,7 +2126,7 @@ static int em_lseg(struct x86_emulate_ctxt *ctxt)
memcpy(&sel, ctxt->src.valptr + ctxt->op_bytes, 2);
rc = load_segment_descriptor(ctxt, sel, seg);
rc = load_segment_descriptor(ctxt, sel, seg, NULL);
if (rc != X86EMUL_CONTINUE)
return rc;
......@@ -2479,19 +2506,19 @@ static int load_state_from_tss16(struct x86_emulate_ctxt *ctxt,
* Now load segment descriptors. If fault happens at this stage
* it is handled in a context of new task
*/
ret = load_segment_descriptor(ctxt, tss->ldt, VCPU_SREG_LDTR);
ret = load_segment_descriptor(ctxt, tss->ldt, VCPU_SREG_LDTR, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES);
ret = load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS);
ret = load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS);
ret = load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS);
ret = load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
......@@ -2620,25 +2647,26 @@ static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
* Now load segment descriptors. If fault happenes at this stage
* it is handled in a context of new task
*/
ret = load_segment_descriptor(ctxt, tss->ldt_selector, VCPU_SREG_LDTR);
ret = load_segment_descriptor(ctxt, tss->ldt_selector, VCPU_SREG_LDTR,
NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES);
ret = load_segment_descriptor(ctxt, tss->es, VCPU_SREG_ES, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS);
ret = load_segment_descriptor(ctxt, tss->cs, VCPU_SREG_CS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS);
ret = load_segment_descriptor(ctxt, tss->ss, VCPU_SREG_SS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS);
ret = load_segment_descriptor(ctxt, tss->ds, VCPU_SREG_DS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->fs, VCPU_SREG_FS);
ret = load_segment_descriptor(ctxt, tss->fs, VCPU_SREG_FS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
ret = load_segment_descriptor(ctxt, tss->gs, VCPU_SREG_GS);
ret = load_segment_descriptor(ctxt, tss->gs, VCPU_SREG_GS, NULL);
if (ret != X86EMUL_CONTINUE)
return ret;
......@@ -2918,24 +2946,37 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
u16 sel, old_cs;
ulong old_eip;
int rc;
struct desc_struct old_desc, new_desc;
const struct x86_emulate_ops *ops = ctxt->ops;
old_cs = get_segment_selector(ctxt, VCPU_SREG_CS);
old_eip = ctxt->_eip;
ops->get_segment(ctxt, &old_cs, &old_desc, NULL, VCPU_SREG_CS);
memcpy(&sel, ctxt->src.valptr + ctxt->op_bytes, 2);
if (load_segment_descriptor(ctxt, sel, VCPU_SREG_CS))
rc = load_segment_descriptor(ctxt, sel, VCPU_SREG_CS, &new_desc);
if (rc != X86EMUL_CONTINUE)
return X86EMUL_CONTINUE;
ctxt->_eip = 0;
memcpy(&ctxt->_eip, ctxt->src.valptr, ctxt->op_bytes);
rc = assign_eip_far(ctxt, ctxt->src.val, new_desc.l);
if (rc != X86EMUL_CONTINUE)
goto fail;
ctxt->src.val = old_cs;
rc = em_push(ctxt);
if (rc != X86EMUL_CONTINUE)
return rc;
goto fail;
ctxt->src.val = old_eip;
return em_push(ctxt);
rc = em_push(ctxt);
/* If we failed, we tainted the memory, but the very least we should
restore cs */
if (rc != X86EMUL_CONTINUE)
goto fail;
return rc;
fail:
ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS);
return rc;
}
static int em_ret_near_imm(struct x86_emulate_ctxt *ctxt)
......@@ -3081,7 +3122,7 @@ static int em_mov_sreg_rm(struct x86_emulate_ctxt *ctxt)
/* Disable writeback. */
ctxt->dst.type = OP_NONE;
return load_segment_descriptor(ctxt, sel, ctxt->modrm_reg);
return load_segment_descriptor(ctxt, sel, ctxt->modrm_reg, NULL);
}
static int em_lldt(struct x86_emulate_ctxt *ctxt)
......@@ -3090,7 +3131,7 @@ static int em_lldt(struct x86_emulate_ctxt *ctxt)
/* Disable writeback. */
ctxt->dst.type = OP_NONE;
return load_segment_descriptor(ctxt, sel, VCPU_SREG_LDTR);
return load_segment_descriptor(ctxt, sel, VCPU_SREG_LDTR, NULL);
}
static int em_ltr(struct x86_emulate_ctxt *ctxt)
......@@ -3099,7 +3140,7 @@ static int em_ltr(struct x86_emulate_ctxt *ctxt)
/* Disable writeback. */
ctxt->dst.type = OP_NONE;
return load_segment_descriptor(ctxt, sel, VCPU_SREG_TR);
return load_segment_descriptor(ctxt, sel, VCPU_SREG_TR, NULL);
}
static int em_invlpg(struct x86_emulate_ctxt *ctxt)
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7