From 8631e01c2c5d1fe6705bcc0d733a0b7a17d3daac Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 27 Jun 2025 12:48:35 +0200 Subject: [PATCH] fanotify: sanitize handle_type values when reporting fid Unlike file_handle, type and len of struct fanotify_fh are u8. Traditionally, filesystem return handle_type < 0xff, but there is no enforecement for that in vfs. Add a sanity check in fanotify to avoid truncating handle_type if its value is > 0xff. Fixes: 7cdafe6cc4a6 ("exportfs: check for error return value from exportfs_encode_*()") Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Link: https://patch.msgid.link/20250627104835.184495-1-amir73il@gmail.com --- fs/notify/fanotify/fanotify.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 3083643b864b..bfe884d624e7 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -454,7 +454,13 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, dwords = fh_len >> 2; type = exportfs_encode_fid(inode, buf, &dwords); err = -EINVAL; - if (type <= 0 || type == FILEID_INVALID || fh_len != dwords << 2) + /* + * Unlike file_handle, type and len of struct fanotify_fh are u8. + * Traditionally, filesystem return handle_type < 0xff, but there + * is no enforecement for that in vfs. + */ + BUILD_BUG_ON(MAX_HANDLE_SZ > 0xff || FILEID_INVALID > 0xff); + if (type <= 0 || type >= FILEID_INVALID || fh_len != dwords << 2) goto out_err; fh->type = type; -- 2.25.1