linux-kernel - [tip:x86/urgent] i386/audit: stop scribbling on the stack frame

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 24 Oct 2014 13:31:16 -0700
From:	tip-bot for Eric Paris <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	przanoni@...il.com, linux-kernel@...r.kernel.org,
	eparis@...hat.com, rgb@...hat.com, hpa@...or.com, mingo@...nel.org,
	tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/urgent] i386/audit: stop scribbling on the stack frame

Commit-ID:  26c2d2b39128adba276d140eefa2745591b88536
Gitweb:     http://git.kernel.org/tip/26c2d2b39128adba276d140eefa2745591b88536
Author:     Eric Paris <eparis@...hat.com>
AuthorDate: Thu, 23 Oct 2014 00:04:03 -0400
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Fri, 24 Oct 2014 13:27:56 -0700

i386/audit: stop scribbling on the stack frame

git commit b4f0d3755c5e9cc86292d5fd78261903b4f23d4a was very very dumb.
It was writing over %esp/pt_regs semi-randomly on i686  with the expected
"system can't boot" results.  As noted in:

https://bugs.freedesktop.org/show_bug.cgi?id=85277

This patch stops fscking with pt_regs.  Instead it sets up the registers
for the call to __audit_syscall_entry in the most obvious conceivable
way.  It then does just a tiny tiny touch of magic.  We need to get what
started in PT_EDX into 0(%esp) and PT_ESI into 4(%esp).  This is as easy
as a pair of pushes.

After the call to __audit_syscall_entry all we need to do is get that
now useless junk off the stack (pair of pops) and reload %eax with the
original syscall so other stuff can keep going about it's business.

Reported-by: Paulo Zanoni <przanoni@...il.com>
Signed-off-by: Eric Paris <eparis@...hat.com>
Link: http://lkml.kernel.org/r/1414037043-30647-1-git-send-email-eparis@redhat.com
Cc: Richard Guy Briggs <rgb@...hat.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/kernel/entry_32.S | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index b553ed8..344b63f 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -447,15 +447,14 @@ sysenter_exit:
 sysenter_audit:
 	testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
 	jnz syscall_trace_entry
-	addl $4,%esp
-	CFI_ADJUST_CFA_OFFSET -4
-	movl %esi,4(%esp)		/* 5th arg: 4th syscall arg */
-	movl %edx,(%esp)		/* 4th arg: 3rd syscall arg */
-	/* %ecx already in %ecx		   3rd arg: 2nd syscall arg */
-	movl %ebx,%edx			/* 2nd arg: 1st syscall arg */
-	/* %eax already in %eax		   1st arg: syscall number */
+	/* movl PT_EAX(%esp), %eax	already set, syscall number: 1st arg to audit */
+	movl PT_EBX(%esp), %edx		/* ebx/a0: 2nd arg to audit */
+	/* movl PT_ECX(%esp), %ecx	already set, a1: 3nd arg to audit */
+	pushl_cfi PT_ESI(%esp)		/* a3: 5th arg */
+	pushl_cfi PT_EDX+4(%esp)	/* a2: 4th arg */
 	call __audit_syscall_entry
-	pushl_cfi %ebx
+	popl_cfi %ecx /* get that remapped edx off the stack */
+	popl_cfi %ecx /* get that remapped esi off the stack */
 	movl PT_EAX(%esp),%eax		/* reload syscall number */
 	jmp sysenter_do_call
 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/