[PATCH, resend] x86-64: fix register leak in 32-bit syscall audting

[PATCH, resend] x86-64: fix register leak in 32-bit syscall audting

[Jan Beulich]

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 <jbeulich@novell.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: <stable@kernel.org>

---
 arch/x86/ia32/ia32entry.S |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- linux-2.6.32-rc5/arch/x86/ia32/ia32entry.S	2009-10-19 13:12:43.000000000 +0200
+++ 2.6.32-rc5-x86_64-ia32-syscall-audit-ebp/arch/x86/ia32/ia32entry.S	2009-10-19 09:36:39.000000000 +0200
@@ -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:

[tip:x86/urgent] x86-64: Fix register leak in 32-bit syscall audting

[tip-bot for Jan Beulich]

Commit-ID:  81766741fe1eee3884219e8daaf03f466f2ed52f
Gitweb:     http://git.kernel.org/tip/81766741fe1eee3884219e8daaf03f466f2ed52f
Author:     Jan Beulich <JBeulich@novell.com>
AuthorDate: Mon, 26 Oct 2009 15:20:29 +0000
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 26 Oct 2009 16:23:26 +0100

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 <jbeulich@novell.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: <stable@kernel.org>
LKML-Reference: <4AE5CC4D020000780001BD13@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/ia32/ia32entry.S |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

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: