linux-kernel - [PATCH v2 5/7] x86, fpu: copy_process: sanitize fpu->last

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: <20140902175727.GA21666@redhat.com>
Date:	Tue, 2 Sep 2014 19:57:27 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Suresh Siddha <sbsiddha@...il.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Bean Anderson <bean@...lsystems.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/7] x86, fpu: copy_process: sanitize fpu->last_cpu
	initialization

Cosmetic, but imho memset(&dst->thread.fpu, 0) is not good simply
because it hides the (important) usage of ->has_fpu/etc from grep.
Change this code to initialize the members explicitly.

And note that ->last_cpu = 0 looks simply wrong, this can confuse
fpu_lazy_restore() if per_cpu(fpu_owner_task, 0) has already exited
and copy_process() re-allocated the same task_struct. Fortunately
this is not actually possible because child->fpu_counter == 0 and
thus fpu_lazy_restore() will not be called, but still this is not
clean/robust.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Suresh Siddha <sbsiddha@...il.com>
---
 arch/x86/kernel/process.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1dfdd69..9b9f088 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -66,7 +66,9 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
 	*dst = *src;
 
-	memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu));
+	dst->thread.fpu.has_fpu = 0;
+	dst->thread.fpu.last_cpu = ~0;
+	dst->thread.fpu.state = NULL;
 	if (tsk_used_math(src)) {
 		int err = fpu_alloc(&dst->thread.fpu);
 		if (err)
-- 
1.5.5.1

--
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/