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ksmbd: fix out-of-bound read in deassemble_neg_contexts()

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commit f1a411873c85b642f13b01f21b534c2bab81fc1b upstream.

The check in the beginning is
`clen + sizeof(struct smb2_neg_context) <= len_of_ctxts`,
but in the end of loop, `len_of_ctxts` will subtract
`((clen + 7) & ~0x7) + sizeof(struct smb2_neg_context)`, which causes
integer underflow when clen does the 8 alignment. We should use
`(clen + 7) & ~0x7` in the check to avoid underflow from happening.

Then there are some variables that need to be declared unsigned
instead of signed.

[   11.671070] BUG: KASAN: slab-out-of-bounds in smb2_handle_negotiate+0x799/0x1610
[   11.671533] Read of size 2 at addr ffff888005e86cf2 by task kworker/0:0/7
...
[   11.673383] Call Trace:
[   11.673541]  <TASK>
[   11.673679]  dump_stack_lvl+0x33/0x50
[   11.673913]  print_report+0xcc/0x620
[   11.674671]  kasan_report+0xae/0xe0
[   11.675171]  kasan_check_range+0x35/0x1b0
[   11.675412]  smb2_handle_negotiate+0x799/0x1610
[   11.676217]  ksmbd_smb_negotiate_common+0x526/0x770
[   11.676795]  handle_ksmbd_work+0x274/0x810
...

Cc: stable@vger.kernel.org
Signed-off-by: Chih-Yen Chang <cc85nod@gmail.com>
Tested-by: Chih-Yen Chang <cc85nod@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Namjae Jeon 2023-05-28 00:23:09 +09:00 committed by Greg Kroah-Hartman
parent fb322da83c
commit bf12d7fb63
1 changed files with 6 additions and 7 deletions
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13
fs/ksmbd/smb2pdu.c
View File

@ -979,13 +979,13 @@ static void decode_sign_cap_ctxt(struct ksmbd_conn *conn,
static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
struct smb2_negotiate_req *req,
int len_of_smb)
unsigned int len_of_smb)
{
/* +4 is to account for the RFC1001 len field */
struct smb2_neg_context *pctx = (struct smb2_neg_context *)req;
int i = 0, len_of_ctxts;
int offset = le32_to_cpu(req->NegotiateContextOffset);
int neg_ctxt_cnt = le16_to_cpu(req->NegotiateContextCount);
unsigned int offset = le32_to_cpu(req->NegotiateContextOffset);
unsigned int neg_ctxt_cnt = le16_to_cpu(req->NegotiateContextCount);
__le32 status = STATUS_INVALID_PARAMETER;
ksmbd_debug(SMB, "decoding %d negotiate contexts\n", neg_ctxt_cnt);
@ -999,7 +999,7 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
while (i++ < neg_ctxt_cnt) {
int clen, ctxt_len;
if (len_of_ctxts < sizeof(struct smb2_neg_context))
if (len_of_ctxts < (int)sizeof(struct smb2_neg_context))
break;
pctx = (struct smb2_neg_context *)((char *)pctx + offset);
@ -1054,9 +1054,8 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
}
/* offsets must be 8 byte aligned */
clen = (clen + 7) & ~0x7;
offset = clen + sizeof(struct smb2_neg_context);
len_of_ctxts -= clen + sizeof(struct smb2_neg_context);
offset = (ctxt_len + 7) & ~0x7;
len_of_ctxts -= offset;
}
return status;
}