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io_uring/rsrc: don't rely on user vaddr alignment

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Commit 3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b upstream.

There is no guaranteed alignment for user pointers, however the
calculation of an offset of the first page into a folio after coalescing
uses some weird bit mask logic, get rid of it.

Cc: stable@vger.kernel.org
Reported-by: David Hildenbrand <david@redhat.com>
Fixes: a8edbb424b ("io_uring/rsrc: enable multi-hugepage buffer coalescing")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/io-uring/e387b4c78b33f231105a601d84eefd8301f57954.1750771718.git.asml.silence@gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov
2025-06-24 14:40:34 +01:00
committed by Greg Kroah-Hartman
parent 53fd75f25b
commit 50998b0ae7
2 changed files with 5 additions and 1 deletions
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5
io_uring/rsrc.c
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@@ -918,6 +918,7 @@ static bool io_try_coalesce_buffer(struct page ***pages, int *nr_pages,
return false;
data->folio_shift = folio_shift(folio);
data->first_folio_page_idx = folio_page_idx(folio, page_array[0]);
/*
* Check if pages are contiguous inside a folio, and all folios have
* the same page count except for the head and tail.
@@ -998,7 +999,9 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
if (coalesced)
imu->folio_shift = data.folio_shift;
refcount_set(&imu->refs, 1);
off = (unsigned long) iov->iov_base & ((1UL << imu->folio_shift) - 1);
off = (unsigned long)iov->iov_base & ~PAGE_MASK;
if (coalesced)
off += data.first_folio_page_idx << PAGE_SHIFT;
*pimu = imu;
ret = 0;

1
io_uring/rsrc.h
View File

@@ -56,6 +56,7 @@ struct io_imu_folio_data {
/* For non-head/tail folios, has to be fully included */
unsigned int nr_pages_mid;
unsigned int folio_shift;
unsigned long first_folio_page_idx;
};
void io_rsrc_node_ref_zero(struct io_rsrc_node *node);