Add comment to elaborate why mmap_sem for is used by prctl. Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> --- akpm: this patch can be foled into: mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct.patch kernel/sys.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sys.c b/kernel/sys.c index 0cc5a1c..943fdc5 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2011,6 +2011,10 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data return error; } + /* + * arg_lock protects concurent updates but we still need mmap_sem for + * read to exclude races with sys_brk. + */ down_read(&mm->mmap_sem); /* -- 1.8.3.1
