[PATCH v5 6/6] smb: client: preserve create-context parsing errors

[Zihan Xi]

smb2_compound_op() saves the result from compound_send_recv() in
tmp_rc. For SMB2_OP_OPEN_QUERY it then parses the CREATE contexts, but
the final assignment of rc from tmp_rc discards a parsing error. A
malformed create-context response can therefore be reported as
successful to smb2_query_path_info().

Keep a create-context parsing error in tmp_rc so it survives per-command
response processing and is returned to the caller.

Fixes: b07687edee99 ("cifs: Improve SMB2+ stat() to work also without FILE_READ_ATTRIBUTES")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Vega <vega@xxxxxxxxxx>
Assisted-by: LLM
Co-developed-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Luxing Yin <root@xxxxxxxxxx>
Signed-off-by: Zihan Xi <zihanx@xxxxxxxxxx>
---
changes in v5:
  - Rerolled the series after fixing a NULL dereference reported by the
    kernel test robot Smatch analysis in patch 5:
    https://lore.kernel.org/r/202609241449.HlHmnZFZ-lkp@xxxxxxxxx/
  - v4 Link: https://lore.kernel.org/all/cover.1789478666.git.zihanx@xxxxxxxxxx/
changes in v4:
  - Keep a create-context parsing error in tmp_rc while processing later
    compound responses.
  - v3 Link: https://lore.kernel.org/all/cover.1788516372.git.zihanx@xxxxxxxxxx/
changes in v3:
  - No counterpart; this patch is added in the v4 reroll.
  - v2 Link: https://lore.kernel.org/all/cover.1787486936.git.zihanx@xxxxxxxxxx/
changes in v2:
  - No counterpart in v2.
  - v1 Link: https://lore.kernel.org/all/eb1bc35611f91bd10a4772400b37fac26f660956.1782579150.git.xizh2024@xxxxxxxxxx/

---
 fs/smb/client/smb2inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index 6971496dfe8c2..cedad9daeb220 100644
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -582,8 +582,10 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon,
 		/* smb2_parse_contexts() fills idata->fi.IndexNumber */
 		rc = smb2_parse_contexts(server, &rsp_iov[0], &oparms->fid->epoch,
 					 oparms->fid->lease_key, &oplock, &idata->fi, NULL);
-		if (rc)
+		if (rc) {
 			cifs_dbg(VFS, "rc: %d parsing context of compound op\n", rc);
+			tmp_rc = rc;
+		}
 	}
 
 	for (i = 0; i < num_cmds; i++) {
-- 
2.43.0