f2fs: fix KMSAN uninit-value in extent_info usage

KMSAN reported a use of uninitialized value in `__is_extent_mergeable()`
 and `__is_back_mergeable()` via the read extent tree path.

The root cause is that `get_read_extent_info()` only initializes three
fields (`fofs`, `blk`, `len`) of `struct extent_info`, leaving the
remaining fields uninitialized. This leads to undefined behavior
when those fields are accessed later, especially during
extent merging.

Fix it by zero-initializing the `extent_info` struct before population.

Reported-by: syzbot+b8c1d60e95df65e827d4@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b8c1d60e95df65e827d4
Fixes: 94afd6d6e525 ("f2fs: extent cache: support unaligned extent")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index cfe925a3d5555f84a678226050eb171331e37b4b..4ce19a310f38a5a9ec2a102588328b9172fe739f 100644 (file)
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -414,7 +414,7 @@ void f2fs_init_read_extent_tree(struct inode *inode, struct folio *ifolio)
        struct f2fs_extent *i_ext = &F2FS_INODE(&ifolio->page)->i_ext;
        struct extent_tree *et;
        struct extent_node *en;
-       struct extent_info ei;
+       struct extent_info ei = {0};
 
        if (!__may_extent_tree(inode, EX_READ)) {
                /* drop largest read extent */