From: Ryusuke Konishi konishi.ryusuke@gmail.com

stable inclusion from stable-v6.6.54 commit 21839b6fbc3c41b3e374ecbdb0cabbbb2c53cf34 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYPKK CVE: CVE-2024-47699

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit 9403001ad65ae4f4c5de368bdda3a0636b51d51a ]

Patch series "nilfs2: fix potential issues with empty b-tree nodes".

This series addresses three potential issues with empty b-tree nodes that can occur with corrupted filesystem images, including one recently discovered by syzbot.

This patch (of 3):

If a b-tree is broken on the device, and the b-tree height is greater than 2 (the level of the root node is greater than 1) even if the number of child nodes of the b-tree root is 0, a NULL pointer dereference occurs in nilfs_btree_prepare_insert(), which is called from nilfs_btree_insert().

This is because, when the number of child nodes of the b-tree root is 0, nilfs_btree_do_lookup() does not set the block buffer head in any of path[x].bp_bh, leaving it as the initial value of NULL, but if the level of the b-tree root node is greater than 1, nilfs_btree_get_nonroot_node(), which accesses the buffer memory of path[x].bp_bh, is called.

Fix this issue by adding a check to nilfs_btree_root_broken(), which performs sanity checks when reading the root node from the device, to detect this inconsistency.

Thanks to Lizhi Xu for trying to solve the bug and clarifying the cause early on.

Link: https://lkml.kernel.org/r/20240904081401.16682-1-konishi.ryusuke@gmail.com Link: https://lkml.kernel.org/r/20240902084101.138971-1-lizhi.xu@windriver.com Link: https://lkml.kernel.org/r/20240904081401.16682-2-konishi.ryusuke@gmail.com Fixes: 17c76b0104e4 ("nilfs2: B-tree based block mapping") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+9bff4c7b992038a7409f@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9bff4c7b992038a7409f Cc: Lizhi Xu lizhi.xu@windriver.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Zhang Kunbo zhangkunbo@huawei.com --- fs/nilfs2/btree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c index 598f05867059..fa51ed649968 100644 --- a/fs/nilfs2/btree.c +++ b/fs/nilfs2/btree.c @@ -381,7 +381,8 @@ static int nilfs_btree_root_broken(const struct nilfs_btree_node *node, if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN || level >= NILFS_BTREE_LEVEL_MAX || nchildren < 0 || - nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) { + nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX || + (nchildren == 0 && level > NILFS_BTREE_LEVEL_NODE_MIN))) { nilfs_crit(inode->i_sb, "bad btree root (ino=%lu): level = %d, flags = 0x%x, nchildren = %d", inode->i_ino, level, flags, nchildren);