FAILED: patch "[PATCH] io_uring/rsrc: don't rely on user vaddr alignment" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025062902-emphasize-calzone-a702@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3a3c6d61577dbb23c09df3e21f6f9eda1ecd634b Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Tue, 24 Jun 2025 14:40:34 +0100
Subject: [PATCH] io_uring/rsrc: don't rely on user vaddr alignment

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: a8edbb424b139 ("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>

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 0c09e38784c9..afc67530f912 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -734,6 +734,7 @@ bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
 
 	data->nr_pages_mid = folio_nr_pages(folio);
 	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
@@ -827,7 +828,11 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 	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;
+
 	node->buf = imu;
 	ret = 0;
 
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 0d2138f16322..25e7e998dcfd 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -49,6 +49,7 @@ struct io_imu_folio_data {
 	unsigned int	nr_pages_mid;
 	unsigned int	folio_shift;
 	unsigned int	nr_folios;
+	unsigned long	first_folio_page_idx;
 };
 
 bool io_rsrc_cache_init(struct io_ring_ctx *ctx);