[PATCH 6.1.y] smb: client: do not pass a NULL buf to is_oplock_break()

[Sasha Levin <sashal@kernel.org>]

From: Zikang Gao <2715417602@qq.com>

[ Upstream commit 2225ab306575e424b3dad2ee1be2521c89249d15 ]

receive_encrypted_read() sets *num_mids = 1 and never writes the
caller's bufs[]. Offload returns -1 with *num_mids = 0, so the
demultiplex thread skips the frame. The inline decrypt path
returns 0 even when smb2_find_mid() fails.

cifs_demultiplex_thread() then treats mids[i] == NULL as an
oplock break and calls is_oplock_break(bufs[i], server) with
bufs[i] still NULL. smb2_is_valid_oplock_break() reads
hdr.Command at offset 12 and oopses.

A large encrypted READ whose MessageId does not match is enough
to panic cifsd.

    Oops: general protection fault, probably for non-canonical address
    0xdffffc0000000001: 0000 [#1] SMP KASAN PTI
    KASAN: null-ptr-deref in range
    [0x0000000000000008-0x000000000000000f]
    CPU: 0 PID: 100 Comm: cifsd
    RIP: smb2_is_valid_oplock_break+0xc8/0x2270 [cifs]
    cifs_demultiplex_thread
    Kernel panic - not syncing: Fatal exception

Return -1 when inline decrypt finds no mid, and skip
is_oplock_break() plus the unknown-frame dump when bufs[i]
is NULL. receive_encrypted_standard() already assigns
bufs[*num_mids].

Fixes: c42a6abe3012 ("CIFS: Add capability to decrypt big read responses")
Assisted-by: LLM
Signed-off-by: Zikang Gao <2715417602@qq.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: stable@vger.kernel.org
[ sashal: added braces around the existing NULL-MID branch to include the new assignment ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/smb/client/connect.c | 4 +++-
 fs/smb/client/smb2ops.c | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 157d947846d9b..f765246fa57c7 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1324,12 +1324,14 @@ cifs_demultiplex_thread(void *p)
 					mids[i]->callback(mids[i]);
 
 				release_mid(mids[i]);
-			} else if (server->ops->is_oplock_break &&
+			} else if (bufs[i] && server->ops->is_oplock_break &&
 				   server->ops->is_oplock_break(bufs[i],
 								server)) {
 				smb2_add_credits_from_hdr(bufs[i], server);
 				cifs_dbg(FYI, "Received oplock break\n");
 			} else {
+				if (!bufs[i])
+					continue;
 				cifs_server_dbg(VFS, "No task to wake, unknown frame received! NumMids %d\n",
 						atomic_read(&mid_count));
 				cifs_dump_mem("Received Data is: ", bufs[i],
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index a7b884e8c3412..ab7ed90d6fb2b 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -5219,9 +5219,10 @@ receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid,
 		goto free_pages;
 
 	*mid = smb2_find_mid(server, buf);
-	if (*mid == NULL)
+	if (*mid == NULL) {
 		cifs_dbg(FYI, "mid not found\n");
-	else {
+		rc = -1;
+	} else {
 		cifs_dbg(FYI, "mid found\n");
 		(*mid)->decrypted = true;
 		rc = handle_read_data(server, *mid, buf,
-- 
2.53.0