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From: Kalesh Singh <kaleshsingh@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: "Jann Horn" <jannh@google.com>,
	"Jeffrey Vander Stoep" <jeffv@google.com>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Minchan Kim" <minchan@kernel.org>,
	"Hridya Valsaraju" <hridya@google.com>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	"Alexey Dobriyan" <adobriyan@gmail.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Mauro Carvalho Chehab" <mchehab+huawei@kernel.org>,
	"Michal Hocko" <mhocko@suse.com>,
	"Alexey Gladkov" <gladkov.alexey@gmail.com>,
	"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Michel Lespinasse" <walken@google.com>,
	"Bernd Edlinger" <bernd.edlinger@hotmail.de>,
	"Andrei Vagin" <avagin@gmail.com>, "Helge Deller" <deller@gmx.de>,
	"James Morris" <jamorris@linux.microsoft.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
Subject: Re: [RESEND PATCH v6 1/2] procfs: Allow reading fdinfo with PTRACE_MODE_READ
Date: Wed, 17 Mar 2021 23:14:08 -0700	[thread overview]
Message-ID: <CAC_TJvcWuzb3FPqYQ_LYJ1iEbTWQE=E=hYaLme3VCZFBQNGe0w@mail.gmail.com> (raw)
In-Reply-To: <202103172255.46B192DA@keescook>

On Wed, Mar 17, 2021 at 10:55 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Mar 08, 2021 at 05:06:40PM +0000, Kalesh Singh wrote:
> > Android captures per-process system memory state when certain low memory
> > events (e.g a foreground app kill) occur, to identify potential memory
> > hoggers. In order to measure how much memory a process actually consumes,
> > it is necessary to include the DMA buffer sizes for that process in the
> > memory accounting. Since the handle to DMA buffers are raw FDs, it is
> > important to be able to identify which processes have FD references to
> > a DMA buffer.
> >
> > Currently, DMA buffer FDs can be accounted using /proc/<pid>/fd/* and
> > /proc/<pid>/fdinfo -- both are only readable by the process owner,
> > as follows:
> >   1. Do a readlink on each FD.
> >   2. If the target path begins with "/dmabuf", then the FD is a dmabuf FD.
> >   3. stat the file to get the dmabuf inode number.
> >   4. Read/ proc/<pid>/fdinfo/<fd>, to get the DMA buffer size.
> >
> > Accessing other processes' fdinfo requires root privileges. This limits
> > the use of the interface to debugging environments and is not suitable
> > for production builds.  Granting root privileges even to a system process
> > increases the attack surface and is highly undesirable.
> >
> > Since fdinfo doesn't permit reading process memory and manipulating
> > process state, allow accessing fdinfo under PTRACE_MODE_READ_FSCRED.
> >
> > Suggested-by: Jann Horn <jannh@google.com>
> > Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> Who would be best to pick this up? Maybe akpm?

Thanks Kees. Andrew has queued the patchset for the mm tree.

>
> --
> Kees Cook

      reply	other threads:[~2021-03-18  6:15 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-08 17:06 [RESEND PATCH v6 1/2] procfs: Allow reading fdinfo with PTRACE_MODE_READ Kalesh Singh
2021-03-08 17:06 ` [RESEND PATCH v6 2/2] procfs/dmabuf: Add inode number to /proc/*/fdinfo Kalesh Singh
2021-03-18  5:54   ` Kees Cook
2021-03-08 17:54 ` [RESEND PATCH v6 1/2] procfs: Allow reading fdinfo with PTRACE_MODE_READ Christian König
2021-03-08 18:06   ` Kalesh Singh
2021-03-18  5:55 ` Kees Cook
2021-03-18  6:14   ` Kalesh Singh [this message]

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