From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Paris Subject: Re: [PATCH v1] vfs: fix IMA lockdep circular locking dependency Date: Tue, 24 Jan 2012 13:51:38 -0500 Message-ID: <1327431098.4131.6.camel@localhost> References: <1327426472-25275-1-git-send-email-zohar@linux.vnet.ibm.com> <1327427142.4131.4.camel@localhost> <1327430451.2129.22.camel@falcor> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-security-module@vger.kernel.org, Al Viro , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Mimi Zohar To: Mimi Zohar Return-path: In-Reply-To: <1327430451.2129.22.camel@falcor> Sender: linux-security-module-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue, 2012-01-24 at 13:40 -0500, Mimi Zohar wrote: > On Tue, 2012-01-24 at 12:45 -0500, Eric Paris wrote: > > On Tue, 2012-01-24 at 12:34 -0500, Mimi Zohar wrote: > > > The circular lockdep is caused by allocating the 'iint' for mmapped > > > files. Originally when an 'iint' was allocated for every inode > > > in inode_alloc_security(), before the inode was accessible, no > > > locking was necessary. Commits bc7d2a3e and 196f518 changed this > > > behavior and allocated the 'iint' on a per need basis, resulting in > > > the mmap_sem being taken before the i_mutex for mmapped files. > > > > > > Possible unsafe locking scenario: > > > CPU0 CPU1 > > > ---- ---- > > > lock(&mm->mmap_sem); > > > lock(&sb->s_type->i_mutex_key); > > > lock(&mm->mmap_sem); > > > lock(&sb->s_type->i_mutex_key); > > > > > > The existing security_file_mmap() hook is after the mmap_sem is taken. > > > This patch moves the ima_file_mmap() call from security_file_mmap() to > > > prior to the mmap_sem being taken. > > > > > > Changelog v1: > > > - Instead of just pre-allocating the iint in a new hook, do ALL of the > > > work in the new/moved ima_file_mmap() hook. (Based on Eric Paris' suggestion.) > > > - Removed do_mmap_with_sem() helper function. > > > - export ima_file_mmap() > > > > Why does it need to be exported? What module might call this? > > Without it, I'm getting: > > Kernel: arch/x86/boot/bzImage is ready (#246) > ERROR: "ima_file_mmap" [arch/x86/ia32/ia32_aout.ko] undefined! > make[1]: *** [__modpost] Error 1 > make: *** [modules] Error 2 Ok, that's what I was wondering (and guessing). Sorry! Acked-by: Eric Paris