From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 20 Mar 2018 08:05:00 +0100 From: Greg KH To: "Joel Fernandes (Google)" Cc: Yisheng Xie , devel@driverdev.osuosl.org, Linux Kernel Mailing List , arve@android.com, syzbot+d7a918a7a8e1c952bc36@syzkaller.appspotmail.com, ben@decadent.org.uk Subject: Re: [PATCH] staging: android: ashmem: Fix possible deadlock in ashmem_ioctl Message-ID: <20180320070500.GA3268@kroah.com> References: <1519801162-52182-1-git-send-email-xieyisheng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, Mar 19, 2018 at 03:16:51PM -0700, Joel Fernandes (Google) wrote: > On Tue, Feb 27, 2018 at 10:59 PM, Yisheng Xie wrote: > > ashmem_mutex may create a chain of dependencies like: > > > > CPU0 CPU1 > > mmap syscall ioctl syscall > > -> mmap_sem (acquired) -> ashmem_ioctl > > -> ashmem_mmap -> ashmem_mutex (acquired) > > -> ashmem_mutex (try to acquire) -> copy_from_user > > -> mmap_sem (try to acquire) > > > > There is a lock odering problem between mmap_sem and ashmem_mutex causing > > a lockdep splat[1] during a syzcaller test. This patch fixes the problem > > by move copy_from_user out of ashmem_mutex. > > > > [1] https://www.spinics.net/lists/kernel/msg2733200.html > > > > Fixes: ce8a3a9e76d0 (staging: android: ashmem: Fix a race condition in pin ioctls) > > Reported-by: syzbot+d7a918a7a8e1c952bc36@syzkaller.appspotmail.com > > Signed-off-by: Yisheng Xie > > Greg, > Could you take this patch for the stable trees? I do see it in staging > already. I couldn't find it in stable so wanted to bring it to your > attention. If you already aware of it, please ignore my note. Ah, I didn't realize this needed to be added to the stable trees, I'll queue it up after this current round of releases happen in a few days. thanks, greg k-h