The patch titled
Subject: mm/gup: do not return 0 from pin_user_pages_fast() for bad args
has been added to the -mm mm-unstable branch. Its filename is
mm-gup-do-not-return-0-from-pin_user_pages_fast-for-bad-args.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-do-not-return-0-from-pin_user_pages_fast-for-bad-args.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: Jason Gunthorpe <jgg@xxxxxxxxxx>
Subject: mm/gup: do not return 0 from pin_user_pages_fast() for bad args
Date: Mon, 19 Jun 2023 15:27:25 -0300
These routines are not intended to return zero, the callers cannot do
anything sane with a 0 return. They should return an error which means
future calls to GUP will not succeed, or they should return some non-zero
number of pinned pages which means GUP should be called again.
If start + nr_pages overflows it should return -EOVERFLOW to signal the
arguments are invalid.
Syzkaller keeps tripping on this when fuzzing GUP arguments.
Link: https://lkml.kernel.org/r/0-v1-3d5ed1f20d50+104-gup_overflow_jgg@xxxxxxxxxx
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reported-by: syzbot+353c7be4964c6253f24a@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/000000000000094fdd05faa4d3a4@xxxxxxxxxx
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/gup.c~mm-gup-do-not-return-0-from-pin_user_pages_fast-for-bad-args
+++ a/mm/gup.c
@@ -3080,7 +3080,7 @@ static int internal_get_user_pages_fast(
start = untagged_addr(start) & PAGE_MASK;
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
- return 0;
+ return -EOVERFLOW;
if (end > TASK_SIZE_MAX)
return -EFAULT;
if (unlikely(!access_ok((void __user *)start, len)))
_
Patches currently in -mm which might be from jgg@xxxxxxxxxx are
mm-gup-do-not-return-0-from-pin_user_pages_fast-for-bad-args.patch
