Based on discussions at LPC, this series adds a memory.stat counter for exported dmabufs. This counter allows us to continue tracking system-wide total exported buffer sizes which there is no longer any way to get without DMABUF_SYSFS_STATS, and adds a new capability to track per-cgroup exported buffer sizes. The total (root counter) is helpful for accounting in-kernel dmabuf use (by comparing with the sum of child nodes or with the sum of sizes of mapped buffers or FD references in procfs) in addition to helping identify driver memory leaks when in-kernel use continually increases over time. With per-application cgroups, the per-cgroup counter allows us to quickly see how much dma-buf memory an application has caused to be allocated. This avoids the need to read through all of procfs which can be a lengthy process, and causes the charge to "stick" to the allocating process/cgroup as long as the buffer is alive, regardless of how the buffer is shared (unless the charge is transferred).
The first patch adds the counter to memcg. The next two patches allow the charge for a buffer to be transferred across cgroups which is necessary because of the way most dmabufs are allocated from a central process on Android. The fourth patch adds the binder object flags to the existing selinux_binder_transfer_file LSM hook and a SELinux permission for charge transfers.
[1] https://lore.kernel.org/all/20220617085702.4298-1-christian.koenig@amd.com/
v2: Actually charge memcg vs just mutate the stat counter per Shakeel Butt and Michal Hocko. Shakeel pointed me at the skmem functions which turned out to be very similar to how I was thinking the dmabuf tracking should work. So I've added a pair of dmabuf functions that do essentially the same thing, except conditionally implemented behind CONFIG_MEMCG alongside the other charge/uncharge functions.
Drop security_binder_transfer_charge per Casey Schaufler and Paul Moore
Drop BINDER_FDA_FLAG_XFER_CHARGE (and fix commit message) per Carlos Llamas
Don't expose is_dma_buf_file for use by binder per Hillf Danton
Call dma_buf_stats_teardown in dma_buf_export error handling
Rebase onto v6.2-rc5
Hridya Valsaraju (1): binder: Add flags to relinquish ownership of fds
T.J. Mercier (3): memcg: Track exported dma-buffers dmabuf: Add cgroup charge transfer function security: binder: Add binder object flags to selinux_binder_transfer_file
Documentation/admin-guide/cgroup-v2.rst | 5 ++ drivers/android/binder.c | 27 ++++++++-- drivers/dma-buf/dma-buf.c | 69 +++++++++++++++++++++++++ include/linux/dma-buf.h | 4 ++ include/linux/lsm_hook_defs.h | 2 +- include/linux/lsm_hooks.h | 5 +- include/linux/memcontrol.h | 43 +++++++++++++++ include/linux/security.h | 6 ++- include/uapi/linux/android/binder.h | 19 +++++-- mm/memcontrol.c | 19 +++++++ security/security.c | 4 +- security/selinux/hooks.c | 13 ++++- security/selinux/include/classmap.h | 2 +- 13 files changed, 201 insertions(+), 17 deletions(-)
base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65