From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
To: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [RFC] efivars write(2) races
Date: Fri, 25 Jan 2013 00:25:53 +0000 [thread overview]
Message-ID: <20130125002552.GC4503@ZenIV.linux.org.uk> (raw)
1) process A does write() on efivars file, reaches ->get_variable(),
gets newdatasize set, drops efivars->lock and loses CPU before an attempt to
grab ->i_mutex. process B comes and does the same thing, replacing the
variable contents. Then it grabs ->i_mutex, updates size, drops ->i_mutex
and buggers off. At which point A gets CPU back and proceeds to set size
to whatever would be valid for its write. Only the value is bogus now...
2) what's to prevent EFI_NOT_FOUND being hit twice? Bad things
will obviously happen in that case...
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Matt Fleming <matt.fleming@intel.com>
Cc: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [RFC] efivars write(2) races
Date: Fri, 25 Jan 2013 00:25:53 +0000 [thread overview]
Message-ID: <20130125002552.GC4503@ZenIV.linux.org.uk> (raw)
1) process A does write() on efivars file, reaches ->get_variable(),
gets newdatasize set, drops efivars->lock and loses CPU before an attempt to
grab ->i_mutex. process B comes and does the same thing, replacing the
variable contents. Then it grabs ->i_mutex, updates size, drops ->i_mutex
and buggers off. At which point A gets CPU back and proceeds to set size
to whatever would be valid for its write. Only the value is bogus now...
2) what's to prevent EFI_NOT_FOUND being hit twice? Bad things
will obviously happen in that case...
next reply other threads:[~2013-01-25 0:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-25 0:25 Al Viro [this message]
2013-01-25 0:25 ` [RFC] efivars write(2) races Al Viro
[not found] ` <20130125002552.GC4503-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2013-01-25 3:50 ` Lingzhu Xiang
2013-01-25 3:50 ` Lingzhu Xiang
[not found] ` <51020120.5000500-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-01-25 13:18 ` Matt Fleming
2013-01-25 13:18 ` Matt Fleming
[not found] ` <1359119883.2496.156.camel-ZqTwcBeJ+wsBof6jY8KHXm7IUlhRatedral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2013-01-28 2:38 ` Lingzhu Xiang
2013-01-28 2:38 ` Lingzhu Xiang
[not found] ` <5105E4A3.9040102-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-01-28 12:38 ` Matt Fleming
2013-01-28 12:38 ` Matt Fleming
[not found] ` <1359376730.8282.20.camel-ZqTwcBeJ+wsBof6jY8KHXm7IUlhRatedral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2013-01-29 2:30 ` Lingzhu Xiang
2013-01-29 2:30 ` Lingzhu Xiang
2013-01-25 12:50 ` Matt Fleming
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