ipc: only destroy orphaned shm segments on sysctl write

proc_ipc_dointvec_minmax_orphans() currently calls shm_destroy_orphaned()
whenever shm_rmid_forced is set, including on sysctl reads.  Reading
/proc/sys/kernel/shm_rmid_forced should not take shm_ids rwsem for write
and walk all segments.

Only run the cleanup when the sysctl is written and the forced RMID policy
is enabled.

When shm_rmid_forced=1, monitoring tools that read
/proc/sys/kernel/shm_rmid_forced trigger the cleanup on every read.

Link: https://lore.kernel.org/all/?q=only+destroy+orphaned+shm+segments+on+sysctl+write
Link: https://lore.kernel.org/tencent_738A8BC6E9EA205F555E4B0DAA154D4F8E0A@qq.com
Signed-off-by: Jianlin Shi <shijianlin11@foxmail.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions