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Message-ID: <4FAAEB37.1080001@siemens.com>
Date: Wed, 09 May 2012 19:09:59 -0300
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arch@...r.kernel.org
CC: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Michael Tokarev <mjt@....msk.ru>,
Anthony Liguori <aliguori@...ibm.com>,
Kevin Wolf <kwolf@...hat.com>
Subject: [PATCH] compat: Fix RT signal mask corruption via sigprocmask
compat_sys_sigprocmask reads a smaller signal mask from userspace than
sigprogmask accepts for setting. So the high word of blocked.sig[0] will
be cleared, releasing any potentially blocked RT signal.
This was discovered via userspace code that relies on get/setcontext.
glibc's i386 versions of those functions use sigprogmask instead of
rt_sigprogmask to save/restore the signal mask and caused RT signal
unblocking this way.
Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
kernel/compat.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/kernel/compat.c b/kernel/compat.c
index 74ff849..03e491d 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -381,6 +381,8 @@ asmlinkage long compat_sys_sigprocmask(int how, compat_old_sigset_t __user *set,
if (set && get_user(s, set))
return -EFAULT;
+ s |= current->blocked.sig[0] &
+ ~((old_sigset_t)(compat_old_sigset_t)-1);
old_fs = get_fs();
set_fs(KERNEL_DS);
ret = sys_sigprocmask(how,
--
1.7.3.4
--
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