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Date:	Mon, 26 Oct 2009 15:24:51 GMT
From:	tip-bot for Jan Beulich <>
Subject: [tip:x86/urgent] x86-64: Fix register leak in 32-bit syscall audting

Commit-ID:  81766741fe1eee3884219e8daaf03f466f2ed52f
Author:     Jan Beulich <>
AuthorDate: Mon, 26 Oct 2009 15:20:29 +0000
Committer:  Ingo Molnar <>
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 <>
Acked-by: Roland McGrath <>
Cc: <>
LKML-Reference: <>
Signed-off-by: Ingo Molnar <>
 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 */
-	.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
@@ -217,7 +217,6 @@ sysexit_from_sys_call:
 	call audit_syscall_exit
 	movl RAX-ARGOFFSET(%rsp),%eax	/* reload syscall return value */
-	movl \ebpsave-ARGOFFSET(%rsp),%ebp /* reload user register value */
@@ -351,7 +350,7 @@ cstar_auditsys:
 	jmp cstar_dispatch
-	auditsys_exit sysretl_from_sys_call, RCX /* user %ebp in RCX slot */
+	auditsys_exit sysretl_from_sys_call
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