linux-kernel - [PATCH 5.15 080/530] btrfs: set generation before calling btrfs_clean_tree_block in btrfs_init_new

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Message-Id: <20221024113048.630379815@linuxfoundation.org>
Date:   Mon, 24 Oct 2022 13:27:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot <syzbot+fba8e2116a12609b6c59@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.15 080/530] btrfs: set generation before calling btrfs_clean_tree_block in btrfs_init_new_buffer

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit cbddcc4fa3443fe8cfb2ff8e210deb1f6a0eea38 upstream.

syzbot is reporting uninit-value in btrfs_clean_tree_block() [1], for
commit bc877d285ca3dba2 ("btrfs: Deduplicate extent_buffer init code")
missed that btrfs_set_header_generation() in btrfs_init_new_buffer() must
not be moved to after clean_tree_block() because clean_tree_block() is
calling btrfs_header_generation() since commit 55c69072d6bd5be1 ("Btrfs:
Fix extent_buffer usage when nodesize != leafsize").

Since memzero_extent_buffer() will reset "struct btrfs_header" part, we
can't move btrfs_set_header_generation() to before memzero_extent_buffer().
Just re-add btrfs_set_header_generation() before btrfs_clean_tree_block().

Link: https://syzkaller.appspot.com/bug?extid=fba8e2116a12609b6c59 [1]
Reported-by: syzbot <syzbot+fba8e2116a12609b6c59@...kaller.appspotmail.com>
Fixes: bc877d285ca3dba2 ("btrfs: Deduplicate extent_buffer init code")
CC: stable@...r.kernel.org # 4.19+
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/extent-tree.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4802,6 +4802,9 @@ btrfs_init_new_buffer(struct btrfs_trans
 	    !test_bit(BTRFS_ROOT_RESET_LOCKDEP_CLASS, &root->state))
 		lockdep_owner = BTRFS_FS_TREE_OBJECTID;
 
+	/* btrfs_clean_tree_block() accesses generation field. */
+	btrfs_set_header_generation(buf, trans->transid);
+
 	/*
 	 * This needs to stay, because we could allocate a freed block from an
 	 * old tree into a new tree, so we need to make sure this new block is