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SubjectRe: [PATCH] tmpfs: ensure O_LARGEFILE with generic_file_open()
On 2022-09-28 13:27-0700, Hugh Dickins wrote:
> From: Hugh Dickins <hughd@google.com>
>
> On Wed, 28 Sep 2022, Thomas Weißschuh wrote:
> > From: Thomas Weißschuh <thomas.weissschuh@amadeus.com>
> >
> > Without this check open() will open large files on tmpfs although
> > O_LARGEFILE was not specified. This is inconsistent with other
> > filesystems.
> > Also it will later result in EOVERFLOW on stat() or EFBIG on write().
> >
> > Link: https://lore.kernel.org/lkml/76bedae6-22ea-4abc-8c06-b424ceb39217@t-8ch.de/
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@amadeus.com>
>
> Acked-by: Hugh Dickins <hughd@google.com>
>
> Thanks! I think you deserve some special award for finding and fixing
> such an ancient bug/inconsistency - dating back to early v2.4 it seems.

Seems to be my special talent.

> But only affecting 32-bit; and since we've happily lived with it so long,
> and the fix does change behaviour for userspace, better not to Cc stable.

That was my feeling, too.

> There are some other filesystems still behaving as tmpfs was (ramfs,
> hugetlbfsi, and I didn't look further); but we do make more of an effort
> to keep tmpfs in line with the major filesystems - thank you.

NFS seems also to be affected, which I think warrants a fix.
My plan was to wait for the feedback to this patch and if it works out to then
submit patches for NFS as validating that will be a bit more involved.

> > ---
> > mm/shmem.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/mm/shmem.c b/mm/shmem.c
> > index 42e5888bf84d..902c5550fabc 100644
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -3876,6 +3876,7 @@ EXPORT_SYMBOL(shmem_aops);
> >
> > static const struct file_operations shmem_file_operations = {
> > .mmap = shmem_mmap,
> > + .open = generic_file_open,
> > .get_unmapped_area = shmem_get_unmapped_area,
> > #ifdef CONFIG_TMPFS
> > .llseek = shmem_file_llseek,
> >
> > base-commit: f76349cf41451c5c42a99f18a9163377e4b364ff
> > --
> > 2.37.3

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