[007/131] mm/gup: might_lock_read(mmap_sem) in get_user_pages_fast()

Commit Message

Andrew Morton June 3, 2020, 10:56 p.m. UTC

From: John Hubbard <[e-mail]>
Subject: mm/gup: might_lock_read(mmap_sem) in get_user_pages_fast()

Instead of scattering these assertions across the drivers, do this
assertion inside the core of get_user_pages_fast*() functions.  That also
includes pin_user_pages_fast*() routines.

Add a might_lock_read(mmap_sem) call to internal_get_user_pages_fast().

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: John Hubbard <[e-mail]>
Suggested-by: Matthew Wilcox <[e-mail]>
Reviewed-by: Matthew Wilcox <[e-mail]>
Cc: Michel Lespinasse <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/gup.c |    3 +++
 1 file changed, 3 insertions(+)

Patch

--- a/mm/gup.c~mm-gup-might_lock_readmmap_sem-in-get_user_pages_fast
+++ a/mm/gup.c
@@ -2739,6 +2739,9 @@  static int internal_get_user_pages_fast(
 				       FOLL_FAST_ONLY)))
 		return -EINVAL;
 
+	if (!(gup_flags & FOLL_FAST_ONLY))
+		might_lock_read(&current->mm->mmap_sem);
+
 	start = untagged_addr(start) & PAGE_MASK;
 	addr = start;
 	len = (unsigned long) nr_pages << PAGE_SHIFT;