From: Miquel Sabaté Solà Date: Tue, 21 Oct 2025 09:11:25 +0000 (+0200) Subject: btrfs: fix NULL dereference on root when tracing inode eviction X-Git-Tag: v6.19-rc5~33^2~6 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f157dd661339fc6f5f2b574fe2429c43bd309534;p=thirdparty%2Flinux.git btrfs: fix NULL dereference on root when tracing inode eviction 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 --- 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 "