>From df00b84402fb67d94a9eb6b86633092983cb388c Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 5 Feb 2025 19:02:35 +0100 Subject: [PATCH] ext4: Verify fast symlink length Verify fast symlink length stored in inode->i_size matches the string stored in the inode to avoid surprises from corrupted filesystems. Reported-by: syzbot+48a99e426f29859818c0@syzkaller.appspotmail.com Fixes: bae80473f7b0 ("ext4: use inode_set_cached_link()") Suggested-by: "Darrick J. Wong" Signed-off-by: Jan Kara --- fs/ext4/inode.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 7c54ae5fcbd4..fbda5a67f7f9 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5007,8 +5007,16 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, inode->i_op = &ext4_encrypted_symlink_inode_operations; } else if (ext4_inode_is_fast_symlink(inode)) { inode->i_op = &ext4_fast_symlink_inode_operations; - nd_terminate_link(ei->i_data, inode->i_size, - sizeof(ei->i_data) - 1); + if (inode->i_size == 0 || + inode->i_size >= EXT4_N_BLOCKS * 4 || + strnlen((char *)ei->i_data, inode->i_size + 1) != + inode->i_size) { + ext4_error_inode(inode, function, line, 0, + "invalid fast symlink length %llu", + (unsigned long long)inode->i_size); + ret = -EFSCORRUPTED; + goto bad_inode; + } inode_set_cached_link(inode, (char *)ei->i_data, inode->i_size); } else { -- 2.43.0