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Subject[PATCH v3 57/68] afs: Fix afs_write_end() to handle len > page size
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It is possible for the len argument to afs_write_end() to overrun the end
of the page (len is used to key the size of the page in afs_write_start()
when compound pages become a regular thing).

Fix afs_write_end() to correctly trim the write length so that it doesn't
exceed the end of the page.

Fixes: 3003bbd0697b ("afs: Use the netfs_write_begin() helper")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/162367682522.460125.5652091227576721609.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163819660464.215744.4576104569408497052.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906968632.143852.17508469800625963114.stgit@warthog.procyon.org.uk/ # v2
---

fs/afs/write.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 8e4e87d66855..9db3ddb1c45b 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -120,6 +120,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
_enter("{%llx:%llu},{%lx}",
vnode->fid.vid, vnode->fid.vnode, folio_index(folio));

+ len = min_t(size_t, len, folio_size(folio) - from);
if (!folio_test_uptodate(folio)) {
if (copied < len) {
copied = 0;

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