From 9f96e3638b18cf5f3325faa7bcb5dad25ba74216 Mon Sep 17 00:00:00 2001 From: Lizhi Xu Date: Tue, 11 Mar 2025 08:51:19 +0900 Subject: [PATCH] btrfs: add a sanity check for btrfs root in btrfs_search_slot() BugLink: https://bugs.launchpad.net/bugs/2101915 [ Upstream commit 3ed51857a50f530ac7a1482e069dfbd1298558d4 ] Syzbot reports a null-ptr-deref in btrfs_search_slot(). The reproducer is using rescue=ibadroots, and the extent tree root is corrupted thus the extent tree is NULL. When scrub tries to search the extent tree to gather the needed extent info, btrfs_search_slot() doesn't check if the target root is NULL or not, resulting the null-ptr-deref. Add sanity check for btrfs root before using it in btrfs_search_slot(). Reported-by: syzbot+3030e17bd57a73d39bd7@syzkaller.appspotmail.com Fixes: 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots") Link: https://syzkaller.appspot.com/bug?extid=3030e17bd57a73d39bd7 CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Qu Wenruo Tested-by: syzbot+3030e17bd57a73d39bd7@syzkaller.appspotmail.com Signed-off-by: Lizhi Xu Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin CVE-2024-56774 Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- fs/btrfs/ctree.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index fb35597d441f..7406685ff2ae 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2030,7 +2030,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, const struct btrfs_key *key, struct btrfs_path *p, int ins_len, int cow) { - struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_fs_info *fs_info; struct extent_buffer *b; int slot; int ret; @@ -2043,6 +2043,10 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, int min_write_lock_level; int prev_cmp; + if (!root) + return -EINVAL; + + fs_info = root->fs_info; might_sleep(); lowest_level = p->lowest_level;