[PATCH v2 2/2] ksmbd: skip metadata-only stream opens in the delete check

[Ian Bridges <icb@fastmail.org>]

A metadata-only named-stream open without FILE_SHARE_DELETE blocks a
later DELETE open of the file. It also blocks setting the file delete
pending.

Ignore a stream open unless its effective access includes data, execute
or delete access. Reuse the sharing-access helper so overwriting a
stream, or creating one on an existing file, still counts as
FILE_WRITE_DATA. The Time Machine AFP_AfpInfo synthesis keeps only its
requested access.

Fixes: 19043971c947 ("ksmbd: honor stream delete sharing for base file")
Cc: stable@vger.kernel.org
Signed-off-by: Ian Bridges <icb@fastmail.org>
---

Notes:
    This affects shares that use "vfs objects = streams_xattr".
    
    Tested on ksmbd-for-next 957772008502 with KASAN. Targeted stream tests
    and a KUnit matrix covered metadata-only, create and overwrite cases.
    smbtorture matched the base. There were no KASAN reports or warnings.
    
    A reproducer is available on request.
    
    This fix was developed with LLM assistance.

 fs/smb/server/vfs_cache.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c
index f9079c529d07..c846023e5ada 100644
--- a/fs/smb/server/vfs_cache.c
+++ b/fs/smb/server/vfs_cache.c
@@ -420,7 +420,12 @@ bool ksmbd_has_stream_without_delete_share(struct ksmbd_file *fp)
 		if (file_inode(fp->filp) != file_inode(prev_fp->filp))
 			continue;
 
-		if (!(prev_fp->saccess & FILE_SHARE_DELETE_LE)) {
+		/*
+		 * A stream open with no right in FILE_SHARE_CHECKED_ACCESS_LE,
+		 * implied writes included, never conflicts.
+		 */
+		if (!(prev_fp->saccess & FILE_SHARE_DELETE_LE) &&
+		    ksmbd_sharing_daccess(prev_fp) & FILE_SHARE_CHECKED_ACCESS_LE) {
 			ret = true;
 			break;
 		}
-- 
2.47.3