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| author | Nadav Amit <namit@cs.technion.ac.il> | 2014-10-28 01:03:43 +0300 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-11-18 13:28:01 +0300 |
| commit | e4bcfa44c82cb5bcfb44a4722c80686096c2e181 (patch) | |
| tree | 48a9eb647b7782bf0abc297cfbd81af41f2b65a8 /arch/x86 | |
| parent | 4c6a0e0edfe824edd777a496f46817b4fb465cbd (diff) | |
| download | linux-e4bcfa44c82cb5bcfb44a4722c80686096c2e181.tar.xz | |
KVM: x86: Fix far-jump to non-canonical check
commit 7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2 upstream.
Commit d1442d85cc30 ("KVM: x86: Handle errors when RIP is set during far
jumps") introduced a bug that caused the fix to be incomplete. Due to
incorrect evaluation, far jump to segment with L bit cleared (i.e., 32-bit
segment) and RIP with any of the high bits set (i.e, RIP[63:32] != 0) set may
not trigger #GP. As we know, this imposes a security problem.
In addition, the condition for two warnings was incorrect.
Fixes: d1442d85cc30ea75f7d399474ca738e0bc96f715
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
[Add #ifdef CONFIG_X86_64 to avoid complaints of undefined behavior. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 8216f484398f..ffae11d0754a 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -582,12 +582,14 @@ static inline int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst, case 4: ctxt->_eip = (u32)dst; break; +#ifdef CONFIG_X86_64 case 8: if ((cs_l && is_noncanonical_address(dst)) || - (!cs_l && (dst & ~(u32)-1))) + (!cs_l && (dst >> 32) != 0)) return emulate_gp(ctxt, 0); ctxt->_eip = dst; break; +#endif default: WARN(1, "unsupported eip assignment size\n"); } @@ -2000,7 +2002,7 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt) rc = assign_eip_far(ctxt, ctxt->src.val, new_desc.l); if (rc != X86EMUL_CONTINUE) { - WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64); + 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; @@ -2084,7 +2086,7 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) return rc; rc = assign_eip_far(ctxt, eip, new_desc.l); if (rc != X86EMUL_CONTINUE) { - WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64); + WARN_ON(ctxt->mode != X86EMUL_MODE_PROT64); ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS); } return rc; |