From d320f160aa5ff36cdf83c645cca52b615e866e32 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Mon, 2 Mar 2026 09:30:02 -0800 Subject: [PATCH] iomap: reject delalloc mappings during writeback Filesystems should never provide a delayed allocation mapping to writeback; they're supposed to allocate the space before replying. This can lead to weird IO errors and crashes in the block layer if the filesystem is being malicious, or if it hadn't set iomap->dev because it's a delalloc mapping. Fix this by failing writeback on delalloc mappings. Currently no filesystems actually misbehave in this manner, but we ought to be stricter about things like that. Cc: stable@vger.kernel.org # v5.5 Fixes: 598ecfbaa742ac ("iomap: lift the xfs writeback code to iomap") Signed-off-by: Darrick J. Wong Link: https://patch.msgid.link/20260302173002.GL13829@frogsfrogsfrogs Reviewed-by: Christoph Hellwig Reviewed-by: Carlos Maiolino Signed-off-by: Christian Brauner --- fs/iomap/ioend.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c index 4d1ef8a2cee9..60546fa14dfe 100644 --- a/fs/iomap/ioend.c +++ b/fs/iomap/ioend.c @@ -215,17 +215,18 @@ ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, struct folio *folio, WARN_ON_ONCE(!folio->private && map_len < dirty_len); switch (wpc->iomap.type) { - case IOMAP_INLINE: - WARN_ON_ONCE(1); - return -EIO; + case IOMAP_UNWRITTEN: + ioend_flags |= IOMAP_IOEND_UNWRITTEN; + break; + case IOMAP_MAPPED: + break; case IOMAP_HOLE: return map_len; default: - break; + WARN_ON_ONCE(1); + return -EIO; } - if (wpc->iomap.type == IOMAP_UNWRITTEN) - ioend_flags |= IOMAP_IOEND_UNWRITTEN; if (wpc->iomap.flags & IOMAP_F_SHARED) ioend_flags |= IOMAP_IOEND_SHARED; if (folio_test_dropbehind(folio))