Patch "io_uring/kbuf: Allow the full buffer id space for provided buffers" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring/kbuf: Allow the full buffer id space for provided buffers

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-kbuf-allow-the-full-buffer-id-space-for-pro.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3d0553aa4249ef3e8f2336e9ce10d6ddb1ada1cb
Author: Gabriel Krisman Bertazi <krisman@xxxxxxx>
Date:   Wed Oct 4 20:05:30 2023 -0400

    io_uring/kbuf: Allow the full buffer id space for provided buffers
    
    [ Upstream commit f74c746e476b9dad51448b9a9421aae72b60e25f ]
    
    nbufs tracks the number of buffers and not the last bgid. In 16-bit, we
    have 2^16 valid buffers, but the check mistakenly rejects the last
    bid. Let's fix it to make the interface consistent with the
    documentation.
    
    Fixes: ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS")
    Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
    Link: https://lore.kernel.org/r/20231005000531.30800-3-krisman@xxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 74a4f9600642f..f6e5ae026e4be 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -19,12 +19,15 @@
 
 #define BGID_ARRAY	64
 
+/* BIDs are addressed by a 16-bit field in a CQE */
+#define MAX_BIDS_PER_BGID (1 << 16)
+
 struct io_provide_buf {
 	struct file			*file;
 	__u64				addr;
 	__u32				len;
 	__u32				bgid;
-	__u16				nbufs;
+	__u32				nbufs;
 	__u16				bid;
 };
 
@@ -289,7 +292,7 @@ int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	tmp = READ_ONCE(sqe->fd);
-	if (!tmp || tmp > USHRT_MAX)
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
 		return -EINVAL;
 
 	memset(p, 0, sizeof(*p));
@@ -332,7 +335,7 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 		return -EINVAL;
 
 	tmp = READ_ONCE(sqe->fd);
-	if (!tmp || tmp > USHRT_MAX)
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
 		return -E2BIG;
 	p->nbufs = tmp;
 	p->addr = READ_ONCE(sqe->addr);
@@ -352,7 +355,7 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 	tmp = READ_ONCE(sqe->off);
 	if (tmp > USHRT_MAX)
 		return -E2BIG;
-	if (tmp + p->nbufs > USHRT_MAX)
+	if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
 		return -EINVAL;
 	p->bid = tmp;
 	return 0;