From f157dd661339fc6f5f2b574fe2429c43bd309534 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Miquel=20Sabat=C3=A9=20Sol=C3=A0?= Date: Tue, 21 Oct 2025 11:11:25 +0200 Subject: [PATCH] btrfs: fix NULL dereference on root when tracing inode eviction MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When evicting an inode the first thing we do is to setup tracing for it, which implies fetching the root's id. But in btrfs_evict_inode() the root might be NULL, as implied in the next check that we do in btrfs_evict_inode(). Hence, we either should set the ->root_objectid to 0 in case the root is NULL, or we move tracing setup after checking that the root is not NULL. Setting the rootid to 0 at least gives us the possibility to trace this call even in the case when the root is NULL, so that's the solution taken here. Fixes: 1abe9b8a138c ("Btrfs: add initial tracepoint support for btrfs") Reported-by: syzbot+d991fea1b4b23b1f6bf8@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=d991fea1b4b23b1f6bf8 Signed-off-by: Miquel Sabaté Solà Reviewed-by: David Sterba Signed-off-by: David Sterba --- include/trace/events/btrfs.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index 7e418f065b945..125bdc166bfed 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -224,7 +224,8 @@ DECLARE_EVENT_CLASS(btrfs__inode, __entry->generation = BTRFS_I(inode)->generation; __entry->last_trans = BTRFS_I(inode)->last_trans; __entry->logged_trans = BTRFS_I(inode)->logged_trans; - __entry->root_objectid = btrfs_root_id(BTRFS_I(inode)->root); + __entry->root_objectid = BTRFS_I(inode)->root ? + btrfs_root_id(BTRFS_I(inode)->root) : 0; ), TP_printk_btrfs("root=%llu(%s) gen=%llu ino=%llu blocks=%llu " -- 2.47.3