diff options
Diffstat (limited to 'system/xen/xsa/xsa202.patch')
| -rw-r--r-- | system/xen/xsa/xsa202.patch | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa202.patch b/system/xen/xsa/xsa202.patch new file mode 100644 index 0000000000..51d38dcba5 --- /dev/null +++ b/system/xen/xsa/xsa202.patch @@ -0,0 +1,75 @@ +From: Jan Beulich <jbeulich@suse.com> +Subject: x86: force EFLAGS.IF on when exiting to PV guests + +Guest kernels modifying instructions in the process of being emulated +for another of their vCPU-s may effect EFLAGS.IF to be cleared upon +next exiting to guest context, by converting the being emulated +instruction to CLI (at the right point in time). Prevent any such bad +effects by always forcing EFLAGS.IF on. And to cover hypothetical other +similar issues, also force EFLAGS.{IOPL,NT,VM} to zero. + +This is XSA-202. + +Signed-off-by: Jan Beulich <jbeulich@suse.com> +Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> +--- + +--- a/xen/arch/x86/x86_64/compat/entry.S ++++ b/xen/arch/x86/x86_64/compat/entry.S +@@ -109,6 +109,8 @@ compat_process_trap: + /* %rbx: struct vcpu, interrupts disabled */ + ENTRY(compat_restore_all_guest) + ASSERT_INTERRUPTS_DISABLED ++ mov $~(X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_VM),%r11d ++ and UREGS_eflags(%rsp),%r11d + .Lcr4_orig: + .skip .Lcr4_alt_end - .Lcr4_alt, 0x90 + .Lcr4_orig_end: +@@ -144,6 +146,8 @@ ENTRY(compat_restore_all_guest) + (.Lcr4_orig_end - .Lcr4_orig), \ + (.Lcr4_alt_end - .Lcr4_alt) + .popsection ++ or $X86_EFLAGS_IF,%r11 ++ mov %r11d,UREGS_eflags(%rsp) + RESTORE_ALL adj=8 compat=1 + .Lft0: iretq + _ASM_PRE_EXTABLE(.Lft0, handle_exception) +--- a/xen/arch/x86/x86_64/entry.S ++++ b/xen/arch/x86/x86_64/entry.S +@@ -40,28 +40,29 @@ restore_all_guest: + testw $TRAP_syscall,4(%rsp) + jz iret_exit_to_guest + ++ movq 24(%rsp),%r11 # RFLAGS ++ andq $~(X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_VM),%r11 ++ orq $X86_EFLAGS_IF,%r11 ++ + /* Don't use SYSRET path if the return address is not canonical. */ + movq 8(%rsp),%rcx + sarq $47,%rcx + incl %ecx + cmpl $1,%ecx +- ja .Lforce_iret ++ movq 8(%rsp),%rcx # RIP ++ ja iret_exit_to_guest + + cmpw $FLAT_USER_CS32,16(%rsp)# CS +- movq 8(%rsp),%rcx # RIP +- movq 24(%rsp),%r11 # RFLAGS + movq 32(%rsp),%rsp # RSP + je 1f + sysretq + 1: sysretl + +-.Lforce_iret: +- /* Mimic SYSRET behavior. */ +- movq 8(%rsp),%rcx # RIP +- movq 24(%rsp),%r11 # RFLAGS + ALIGN + /* No special register assumptions. */ + iret_exit_to_guest: ++ andl $~(X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_VM),24(%rsp) ++ orl $X86_EFLAGS_IF,24(%rsp) + addq $8,%rsp + .Lft0: iretq + _ASM_PRE_EXTABLE(.Lft0, handle_exception) |