On Thu, Jan 28, 2021 at 1:24 PM Kalesh Singh <[email protected]> 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.
>
> This series proposes making the requirement to read fdinfo less strict
> with PTRACE_MODE_READ.
>
Hi everyone,
I will send v2 of this patch series. Please let me know if you have
any other comments or feedback, that should be addressed in the new
version.
Thanks,
Kalesh
> Kalesh Singh (2):
> procfs: Allow reading fdinfo with PTRACE_MODE_READ
> dmabuf: Add dmabuf inode no to fdinfo
>
> drivers/dma-buf/dma-buf.c | 1 +
> fs/proc/base.c | 4 ++--
> fs/proc/fd.c | 15 ++++++++++++++-
> 3 files changed, 17 insertions(+), 3 deletions(-)
>
> --
> 2.30.0.365.g02bc693789-goog
>