From: Nikita Ermakov <sh1r4s3@xxxxxxxxxxxxxxx> Subject: mm/msync: exit early when the flags is an MS_ASYNC and start < vm_start If an unmapped region was found and the flag is MS_ASYNC (without MS_INVALIDATE) there is nothing to do and the result would be always -ENOMEM, so return immediately. Link: https://lkml.kernel.org/r/20201025092901.56399-1-sh1r4s3@xxxxxxxxxxxxxxx Signed-off-by: Nikita Ermakov <sh1r4s3@xxxxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/msync.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/mm/msync.c~mm-msync-exit-early-when-the-flags-is-an-ms_async-and-start-vm_start +++ a/mm/msync.c @@ -55,7 +55,9 @@ SYSCALL_DEFINE3(msync, unsigned long, st goto out; /* * If the interval [start,end) covers some unmapped address ranges, - * just ignore them, but return -ENOMEM at the end. + * just ignore them, but return -ENOMEM at the end. Besides, if the + * flag is MS_ASYNC (w/o MS_INVALIDATE) the result would be -ENOMEM + * anyway and there is nothing left to do, so return immediately. */ mmap_read_lock(mm); vma = find_vma(mm, start); @@ -69,6 +71,8 @@ SYSCALL_DEFINE3(msync, unsigned long, st goto out_unlock; /* Here start < vma->vm_end. */ if (start < vma->vm_start) { + if (flags == MS_ASYNC) + goto out_unlock; start = vma->vm_start; if (start >= end) goto out_unlock; _
