linux-kernel - [PATCH v2 08/14] x86/entry/64: Really create an error-entry-from-usermode code path

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]

Message-Id: <facd78f5111215d0ed7742da3bdbde49dd68a88b.1434654252.git.luto@kernel.org>
Date:	Thu, 18 Jun 2015 12:08:40 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>, paulmck@...ux.vnet.ibm.com,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 08/14] x86/entry/64: Really create an error-entry-from-usermode code path

In 539f51136500 ("x86/asm/entry/64: Disentangle error_entry/exit
gsbase/ebx/usermode code"), I arranged the code slightly wrong --
IRET faults would skip the code path that was intended to execute on
all error entries from user mode.  Fix it up.

This does not fix a bug, but we'll need it, and it slightly shrinks
the code.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/entry_64.S | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 3bb2c4302df1..33acc3dcc281 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1145,7 +1145,11 @@ ENTRY(error_entry)
 	testb	$3, CS+8(%rsp)
 	jz	error_kernelspace
 
-	/* We entered from user mode */
+error_entry_from_usermode:
+	/*
+	 * We entered from user mode or we're pretending to have entered
+	 * from user mode due to an IRET fault.
+	 */
 	SWAPGS
 
 error_entry_done:
@@ -1174,8 +1178,7 @@ error_kernelspace:
 	 * gsbase and proceed.  We'll fix up the exception and land in
 	 * gs_change's error handler with kernel gsbase.
 	 */
-	SWAPGS
-	jmp	error_entry_done
+	jmp	error_entry_from_usermode
 
 bstep_iret:
 	/* Fix truncated RIP */
-- 
2.4.3

--
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/