[PATCH v2 4/5] ksmbd: prevent out of bound read for SMB2_TREE_CONNNECT

[Namjae Jeon <linkinjeon@kernel.org>]

From: Hyunchul Lee <hyc.lee@gmail.com>

if Status is not 0 and PathLength is long,
smb_strndup_from_utf16 could make out of bound
read in smb2_tree_connnect.

This bug can lead an oops looking something like:

[ 1553.882047] BUG: KASAN: slab-out-of-bounds in smb_strndup_from_utf16+0x469/0x4c0 [ksmbd]
[ 1553.882064] Read of size 2 at addr ffff88802c4eda04 by task kworker/0:2/42805
...
[ 1553.882095] Call Trace:
[ 1553.882098]  <TASK>
[ 1553.882101]  dump_stack_lvl+0x49/0x5f
[ 1553.882107]  print_report.cold+0x5e/0x5cf
[ 1553.882112]  ? smb_strndup_from_utf16+0x469/0x4c0 [ksmbd]
[ 1553.882122]  kasan_report+0xaa/0x120
[ 1553.882128]  ? smb_strndup_from_utf16+0x469/0x4c0 [ksmbd]
[ 1553.882139]  __asan_report_load_n_noabort+0xf/0x20
[ 1553.882143]  smb_strndup_from_utf16+0x469/0x4c0 [ksmbd]
[ 1553.882155]  ? smb_strtoUTF16+0x3b0/0x3b0 [ksmbd]
[ 1553.882166]  ? __kmalloc_node+0x185/0x430
[ 1553.882171]  smb2_tree_connect+0x140/0xab0 [ksmbd]
[ 1553.882185]  handle_ksmbd_work+0x30e/0x1020 [ksmbd]
[ 1553.882197]  process_one_work+0x778/0x11c0
[ 1553.882201]  ? _raw_spin_lock_irq+0x8e/0xe0
[ 1553.882206]  worker_thread+0x544/0x1180
[ 1553.882209]  ? __cpuidle_text_end+0x4/0x4
[ 1553.882214]  kthread+0x282/0x320
[ 1553.882218]  ? process_one_work+0x11c0/0x11c0
[ 1553.882221]  ? kthread_complete_and_exit+0x30/0x30
[ 1553.882225]  ret_from_fork+0x1f/0x30
[ 1553.882231]  </TASK>

There is no need to check error request validation in server.
This check allow invalid requests not to validate message.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-17818
Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
---
 v2:
   - add missing fixes and stable tags.

 fs/ksmbd/smb2misc.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/fs/ksmbd/smb2misc.c b/fs/ksmbd/smb2misc.c
index aa1e663d9deb..6e25ace36568 100644
--- a/fs/ksmbd/smb2misc.c
+++ b/fs/ksmbd/smb2misc.c
@@ -90,11 +90,6 @@ static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
 	*off = 0;
 	*len = 0;
 
-	/* error reqeusts do not have data area */
-	if (hdr->Status && hdr->Status != STATUS_MORE_PROCESSING_REQUIRED &&
-	    (((struct smb2_err_rsp *)hdr)->StructureSize) == SMB2_ERROR_STRUCTURE_SIZE2_LE)
-		return ret;
-
 	/*
 	 * Following commands have data areas so we have to get the location
 	 * of the data buffer offset and data buffer length for the particular
-- 
2.25.1