On Wed, Mar 17, 2021 at 10:55 PM Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxxx> > > Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Who would be best to pick this up? Maybe akpm? Thanks Kees. Andrew has queued the patchset for the mm tree. > > -- > Kees Cook
