The patch titled
Subject: mm/gup: make failure to pin an error if FOLL_NOWAIT not specified
has been added to the -mm mm-unstable branch. Its filename is
mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Subject: mm/gup: make failure to pin an error if FOLL_NOWAIT not specified
Date: Tue, 3 Oct 2023 00:14:53 +0100
There really should be no circumstances under which a non-FOLL_NOWAIT GUP
operation fails to return any pages, so make this an error and warn on it.
To catch the trivial case, simply exit early if nr_pages == 0.
This brings __get_user_pages_locked() in line with the behaviour of its
nommu variant.
Link: https://lkml.kernel.org/r/2a42d96dd1e37163f90a0019a541163dafb7e4c3.1696288092.git.lstoakes@xxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Richard Cochran <richardcochran@xxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/mm/gup.c~mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified
+++ a/mm/gup.c
@@ -1471,6 +1471,9 @@ static __always_inline long __get_user_p
long ret, pages_done;
bool must_unlock = false;
+ if (!nr_pages)
+ return 0;
+
/*
* The internal caller expects GUP to manage the lock internally and the
* lock must be released when this returns.
@@ -1595,6 +1598,14 @@ retry:
mmap_read_unlock(mm);
*locked = 0;
}
+
+ /*
+ * Failing to pin anything implies something has gone wrong (except when
+ * FOLL_NOWAIT is specified).
+ */
+ if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
+ return -EFAULT;
+
return pages_done;
}
_
Patches currently in -mm which might be from lstoakes@xxxxxxxxx are
mm-refactor-si_mem_available.patch
mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case.patch
mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case-fix.patch
mm-make-__access_remote_vm-static.patch
mm-gup-explicitly-define-and-check-internal-gup-flags-disallow-foll_touch.patch
mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified.patch
mm-gup-adapt-get_user_page_vma_remote-to-never-return-null.patch
