From f6899bc03cbadc6e308d98252c4a832b5fd45b87 Mon Sep 17 00:00:00 2001 From: Nikita Ermakov Date: Thu, 29 Apr 2021 22:55:41 -0700 Subject: [PATCH] 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@mail.si-head.nl Signed-off-by: Nikita Ermakov Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/msync.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/msync.c b/mm/msync.c index 69c6d2029531..137d1c104f3e 100644 --- a/mm/msync.c +++ b/mm/msync.c @@ -55,7 +55,9 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) 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, start, size_t, len, int, flags) 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;