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-rw-r--r--kernel/sys.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index 775bf8d18d03..2969304c29fe 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2127,9 +2127,15 @@ static int prctl_set_mm(int opt, unsigned long addr,
error = -EINVAL;
- down_write(&mm->mmap_sem);
+ /*
+ * arg_lock protects concurent updates of arg boundaries, we need
+ * mmap_sem for a) concurrent sys_brk, b) finding VMA for addr
+ * validation.
+ */
+ down_read(&mm->mmap_sem);
vma = find_vma(mm, addr);
+ spin_lock(&mm->arg_lock);
prctl_map.start_code = mm->start_code;
prctl_map.end_code = mm->end_code;
prctl_map.start_data = mm->start_data;
@@ -2217,7 +2223,8 @@ static int prctl_set_mm(int opt, unsigned long addr,
error = 0;
out:
- up_write(&mm->mmap_sem);
+ spin_unlock(&mm->arg_lock);
+ up_read(&mm->mmap_sem);
return error;
}