From: Namjae Jeon linkinjeon@kernel.org
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 --- fs/ksmbd/smb2pdu.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
--- a/fs/ksmbd/smb2pdu.c +++ b/fs/ksmbd/smb2pdu.c @@ -991,13 +991,13 @@ static void decode_sign_cap_ctxt(struct
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); @@ -1011,7 +1011,7 @@ static __le32 deassemble_neg_contexts(st 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); @@ -1066,9 +1066,8 @@ static __le32 deassemble_neg_contexts(st }
/* 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; }