[PATCH 5.2 080/162] SMB3: Fix potential memory leak when processing compound chain

Greg Kroah-Hartman
2019-08-27T08:03:02Z

[ Upstream commit 3edeb4a4146dc3b54d6fa71b7ee0585cb52ebfdf ]

When a reconnect happens in the middle of processing a compound chain
the code leaks a buffer from the memory pool. Fix this by properly
checking for a return code and freeing buffers in case of error.

Also maintain a buf variable to be equal to either smallbuf or bigbuf
depending on a response buffer size while parsing a chain and when
returning to the caller.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/smb2ops.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 2ec37dc589a7b..ae10d6e297c3a 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -4015,7 +4015,6 @@ receive_encrypted_standard(struct TCP_Server_Info *server,
{
int ret, length;
char *buf = server->smallbuf;
- char *tmpbuf;
struct smb2_sync_hdr *shdr;
unsigned int pdu_length = server->pdu_size;
unsigned int buf_size;
@@ -4045,18 +4044,15 @@ receive_encrypted_standard(struct TCP_Server_Info *server,
return length;

next_is_large = server->large_buf;
- one_more:
+one_more:
shdr = (struct smb2_sync_hdr *)buf;
if (shdr->NextCommand) {
- if (next_is_large) {
- tmpbuf = server->bigbuf;
+ if (next_is_large)
next_buffer = (char *)cifs_buf_get();
- } else {
- tmpbuf = server->smallbuf;
+ else
next_buffer = (char *)cifs_small_buf_get();
- }
memcpy(next_buffer,
- tmpbuf + le32_to_cpu(shdr->NextCommand),
+ buf + le32_to_cpu(shdr->NextCommand),
pdu_length - le32_to_cpu(shdr->NextCommand));
}

@@ -4085,12 +4081,21 @@ receive_encrypted_standard(struct TCP_Server_Info *server,
pdu_length -= le32_to_cpu(shdr->NextCommand);
server->large_buf = next_is_large;
if (next_is_large)
- server->bigbuf = next_buffer;
+ server->bigbuf = buf = next_buffer;
else
- server->smallbuf = next_buffer;
-
- buf += le32_to_cpu(shdr->NextCommand);
+ server->smallbuf = buf = next_buffer;
goto one_more;
+ } else if (ret != 0) {
+ /*
+ * ret != 0 here means that we didn't get to handle_mid() thus
+ * server->smallbuf and server->bigbuf are still valid. We need
+ * to free next_buffer because it is not going to be used
+ * anywhere.
+ */
+ if (next_is_large)
+ free_rsp_buf(CIFS_LARGE_BUFFER, next_buffer);
+ else
+ free_rsp_buf(CIFS_SMALL_BUFFER, next_buffer);
}

return ret;
--
2.20.1