fs: ext4: initialize fsdata in pagecache_write()

commit 956510c0c7439e90b8103aaeaf4da92878c622f0 upstream.

When aops->write_begin() does not initialize fsdata, KMSAN reports
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Cc: Eric Biggers <ebiggers@kernel.org>
Fixes: c93d8f885809 ("ext4: add basic fs-verity support")
Reported-by: syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221121112134.407362-1-glider@google.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
index 3c640bd..30e3b65 100644 (file)
--- a/fs/ext4/verity.c
+++ b/fs/ext4/verity.c
@@ -79,7 +79,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
                size_t n = min_t(size_t, count,
                                 PAGE_SIZE - offset_in_page(pos));
                struct page *page;
-               void *fsdata;
+               void *fsdata = NULL;
                int res;
 
                res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);