Re: [patch 142/192] procfs: allow reading fdinfo with PTRACE_MODE_READ

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Jun 30, 2021 at 06:54:44PM -0700, Andrew Morton wrote:
> From: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
> Subject: procfs: allow reading fdinfo with PTRACE_MODE_READ
> 
> 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.
> 
> Link: https://lkml.kernel.org/r/20210308170651.919148-1-kaleshsingh@xxxxxxxxxx
> Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
> Suggested-by: Jann Horn <jannh@xxxxxxxxxx>
> Acked-by: Christian König <christian.koenig@xxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> Cc: Alexey Gladkov <gladkov.alexey@xxxxxxxxx>
> Cc: Andrei Vagin <avagin@xxxxxxxxx>
> Cc: Bernd Edlinger <bernd.edlinger@xxxxxxxxxx>
> Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Helge Deller <deller@xxxxxx>
> Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
> Cc: James Morris <jamorris@xxxxxxxxxxxxxxxxxxx>
> Cc: Jeff Vander Stoep <jeffv@xxxxxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Michel Lespinasse <walken@xxxxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: Szabolcs Nagy <szabolcs.nagy@xxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---

Rather useful (also for CRIU and others).
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>



[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux