From 24e35800cdc4350fc34e2bed37b608a9e13ab3b6 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 30 Sep 2009 11:22:11 +0100 Subject: x86: Don't leak 64-bit kernel register values to 32-bit processes While 32-bit processes can't directly access R8...R15, they can gain access to these registers by temporarily switching themselves into 64-bit mode. Therefore, registers not preserved anyway by called C functions (i.e. R8...R11) must be cleared prior to returning to user mode. Signed-off-by: Jan Beulich Cc: LKML-Reference: <4AC34D73020000780001744A@vpn.id2.novell.com> Signed-off-by: Ingo Molnar --- arch/x86/ia32/ia32entry.S | 36 +++++++++++++++++++++++------------- 1 file changed, 23 insertions(+), 13 deletions(-) (limited to 'arch/x86/ia32') diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 74619c4..1733f9f 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -21,8 +21,8 @@ #define __AUDIT_ARCH_LE 0x40000000 #ifndef CONFIG_AUDITSYSCALL -#define sysexit_audit int_ret_from_sys_call -#define sysretl_audit int_ret_from_sys_call +#define sysexit_audit ia32_ret_from_sys_call +#define sysretl_audit ia32_ret_from_sys_call #endif #define IA32_NR_syscalls ((ia32_syscall_end - ia32_sys_call_table)/8) @@ -39,12 +39,12 @@ .endm /* clobbers %eax */ - .macro CLEAR_RREGS _r9=rax + .macro CLEAR_RREGS offset=0, _r9=rax xorl %eax,%eax - movq %rax,R11(%rsp) - movq %rax,R10(%rsp) - movq %\_r9,R9(%rsp) - movq %rax,R8(%rsp) + movq %rax,\offset+R11(%rsp) + movq %rax,\offset+R10(%rsp) + movq %\_r9,\offset+R9(%rsp) + movq %rax,\offset+R8(%rsp) .endm /* @@ -172,6 +172,10 @@ sysexit_from_sys_call: movl RIP-R11(%rsp),%edx /* User %eip */ CFI_REGISTER rip,rdx RESTORE_ARGS 1,24,1,1,1,1 + xorq %r8,%r8 + xorq %r9,%r9 + xorq %r10,%r10 + xorq %r11,%r11 popfq CFI_ADJUST_CFA_OFFSET -8 /*CFI_RESTORE rflags*/ @@ -202,7 +206,7 @@ sysexit_from_sys_call: .macro auditsys_exit exit,ebpsave=RBP testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10) - jnz int_ret_from_sys_call + jnz ia32_ret_from_sys_call TRACE_IRQS_ON sti movl %eax,%esi /* second arg, syscall return value */ @@ -218,8 +222,9 @@ sysexit_from_sys_call: cli TRACE_IRQS_OFF testl %edi,TI_flags(%r10) - jnz int_with_check - jmp \exit + jz \exit + CLEAR_RREGS -ARGOFFSET + jmp int_with_check .endm sysenter_auditsys: @@ -329,6 +334,9 @@ sysretl_from_sys_call: CFI_REGISTER rip,rcx movl EFLAGS-ARGOFFSET(%rsp),%r11d /*CFI_REGISTER rflags,r11*/ + xorq %r10,%r10 + xorq %r9,%r9 + xorq %r8,%r8 TRACE_IRQS_ON movl RSP-ARGOFFSET(%rsp),%esp CFI_RESTORE rsp @@ -353,7 +361,7 @@ cstar_tracesys: #endif xchgl %r9d,%ebp SAVE_REST - CLEAR_RREGS r9 + CLEAR_RREGS 0, r9 movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */ movq %rsp,%rdi /* &pt_regs -> arg1 */ call syscall_trace_enter @@ -425,6 +433,8 @@ ia32_do_call: call *ia32_sys_call_table(,%rax,8) # xxx: rip relative ia32_sysret: movq %rax,RAX-ARGOFFSET(%rsp) +ia32_ret_from_sys_call: + CLEAR_RREGS -ARGOFFSET jmp int_ret_from_sys_call ia32_tracesys: @@ -442,8 +452,8 @@ END(ia32_syscall) ia32_badsys: movq $0,ORIG_RAX-ARGOFFSET(%rsp) - movq $-ENOSYS,RAX-ARGOFFSET(%rsp) - jmp int_ret_from_sys_call + movq $-ENOSYS,%rax + jmp ia32_sysret quiet_ni_syscall: movq $-ENOSYS,%rax -- cgit v1.1 From 81766741fe1eee3884219e8daaf03f466f2ed52f Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 26 Oct 2009 15:20:29 +0000 Subject: x86-64: Fix register leak in 32-bit syscall audting Restoring %ebp after the call to audit_syscall_exit() is not only unnecessary (because the register didn't get clobbered), but in the sysenter case wasn't even doing the right thing: It loaded %ebp from a location below the top of stack (RBP < ARGOFFSET), i.e. arbitrary kernel data got passed back to user mode in the register. Signed-off-by: Jan Beulich Acked-by: Roland McGrath Cc: LKML-Reference: <4AE5CC4D020000780001BD13@vpn.id2.novell.com> Signed-off-by: Ingo Molnar --- arch/x86/ia32/ia32entry.S | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'arch/x86/ia32') diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 1733f9f..581b056 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -204,7 +204,7 @@ sysexit_from_sys_call: movl RDI-ARGOFFSET(%rsp),%r8d /* reload 5th syscall arg */ .endm - .macro auditsys_exit exit,ebpsave=RBP + .macro auditsys_exit exit testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags(%r10) jnz ia32_ret_from_sys_call TRACE_IRQS_ON @@ -217,7 +217,6 @@ sysexit_from_sys_call: call audit_syscall_exit GET_THREAD_INFO(%r10) movl RAX-ARGOFFSET(%rsp),%eax /* reload syscall return value */ - movl \ebpsave-ARGOFFSET(%rsp),%ebp /* reload user register value */ movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi cli TRACE_IRQS_OFF @@ -351,7 +350,7 @@ cstar_auditsys: jmp cstar_dispatch sysretl_audit: - auditsys_exit sysretl_from_sys_call, RCX /* user %ebp in RCX slot */ + auditsys_exit sysretl_from_sys_call #endif cstar_tracesys: -- cgit v1.1