On Mon, Jan 13, 2025 at 05:24:26AM +0100, Christoph Hellwig wrote:
> Commit 32dd4f9c506b ("xfs: remove a superflous hash lookup when inserting
> new buffers") converted xfs_buf_find_insert to use
> rhashtable_lookup_get_insert_fast and thus an operation that returns the
> existing buffer when an insert would duplicate the hash key. But this
> code path misses the check for a buffer with a reference count of zero,
> which could lead to reusing an about to be freed buffer. Fix this by
> using the same atomic_inc_not_zero pattern as xfs_buf_insert.
>
> Fixes: 32dd4f9c506b ("xfs: remove a superflous hash lookup when inserting new buffers")
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.0
and with that added,
Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
--D
> ---
> fs/xfs/xfs_buf.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 6f313fbf7669..f80e39fde53b 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -664,9 +664,8 @@ xfs_buf_find_insert(
> spin_unlock(&bch->bc_lock);
> goto out_free_buf;
> }
> - if (bp) {
> + if (bp && atomic_inc_not_zero(&bp->b_hold)) {
> /* found an existing buffer */
> - atomic_inc(&bp->b_hold);
> spin_unlock(&bch->bc_lock);
> error = xfs_buf_find_lock(bp, flags);
> if (error)
> --
> 2.45.2
>
